HOWARD W. SAMS & COMPANY
COMPUTERFACTS
Technical Service Data
TANDY®
MODEL 1000SX
COMPUTER
FEATURES COMPLETE SCHEMATICS • PRELIMINARY SERVICE CHECKS • TROUBLESHOOTING TIPS
EASY-READ WAVEFORMS • REPLACEMENT PARTS LISTS • SEMICONDUCTOR CROSS REFERENCE
giMfl C COMPUTERFACTS"
TANDY
MODEL 1000SX
PRELIMINARY SERVICE CHECKS
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This data provides the user with a time-saving
service tool which is designed for quick Isola-
tion and repair of Computer system malfunc-
tions.
Check all interconnecting cables for good con-
nection and correct hook-up before making
service checks.
Always turn the Computer Off before connecting
or disconnecting connectors, boards or periph-
erals.
Disconnect al I external peripherals from the
Computer system to eliminate possible external
ma I functions.
Replacement or repair of the Power Supply,
System Board, Keyboard, Disk Drives or con-
nectors may be necessary after the malfunction
has been isolated.
TEST EQUIPMENT AND TOOLS
TEST EQUIPMENMT
Digital Volt/Ohm Meter
Logic Probe
Frequency Counter
Monitor with Audio Input
Disk Drive Tester or Test Program
TOOLS
Head Cleaning Equipment
Contact and Switch Cleaner (non-spray type)
Phillips Screwdriver
Flat Blade Screwdriver
1/4" Socket
IC Insertion and Removal Tools 20, 24 and 40
pin 14, 16, 28
Low Wattage Soldering Iron
Deso I der i ng Eq u I pme nt
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Howard W. Saras & Co.
'm 4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The fisting of any available replacement part herein does not
constitute in any case a recommendation, warranty or guaranty
by Howard W. Sams & Co. as to the quality and suitability of
such replacement part. The numbers of these parts have been
compiled from information furnished to Howard W. Sams & Co.
by the manufacturers of the particular type of replacement part
listed. 87CS19008 DATE 9-87
Reproduction or use, without express permission, of editorial or pic-
torial content, in any manner, is prohibited. No patent liability is
assumed with respect to the use of the information contained herein.
© 1987 Howard W. Sams & Co.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206
U.S.A. Printed in U.S. of America
MISCELLANEOUS ADJUSTMENTS
POWER SUPPLY
NOTE: Do not operate the Power Supply without
a load.
5V ADJUSTMENT
12V ADJUSTMENT
NOTE: Perform the 5V Adjustment first. Con-
nect the Input of a voltmeter to pin 7 of Con-
nector SK3-1. Adjust the 12V Adjust Control
for a voltage of 12.0V.
Connect the Input of a voltmeter to pin 9 of
Connector SK3-1 . Adjust the 5V Adjust Control
(VR1) for a voltage of 5.0V.
VR1 VR2
5V 12V
ADJUST ADJUST
F1
:ib.
CN
(3B)
KEYBOARD
INTERCONNECTING DIAGRAM
II
PRELIMINARY SERVICE CHECKS (Continued)
UAj
v -^ COMPOSITE
AUDIO VIDEO
RGB
VIDEO
/ * ' * * \
( a a m a o )
B1 A1 B1 A1 81 Al B1 A1 B1 A1
J10B J10A
J15
J14
J13
J12
J11
J9
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(8B)
4.77MHz,N0RMAL
7.16MHz,TURB0 J6
12
U51
B31 A31 B31 A31 B31 A31 B31 A31 831 A31
®
SEE SWITCHES
S2 AND JUMPERS'"
U41
ROM (1D)
VIDEO SYSTEM (4C)
RAM 128K v ^
U3B
CPU
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U35
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U24
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(3C) (BE)
R26A
VOLUME
U22
SYSTEM BOARD
LIGHT
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HIGH, TURBO
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J3
J2
RESET
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U37
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BANK 1
BANK
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POWER SUPPLY
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SK3-2
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BOTTOM VIEW
TANDY
MODEL 1000SX
INTERCONNECTING DIAGRAM
PRELIMINARY SERVICE CHECKS (Continued)
LOW. NORMAL
HIGH, TURBO
J4 R26A J1
RAM RAM
BANK1 BANKO
VI
III
PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS
MATCH THE NUMBERS ON THE INTERCONNECTING DIAGRAM AND PHOTOS WITH
THE NUMBERS ON THE SERVICE CHECKS TO BE PERFORMED.
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COMPUTER DEAD
(A) Check for 5.0V at pin 1, -12.0V at
pin 8 and 12.0V at pin 9 of Connec-
tor J6 on the System Board. If the
voltages are correct, go to part
(D). If the voltages are not cor-
rect, check the adjustment of the
5V Adjust (VR1) and 12.0V Adjust
(VR2) Controls on the Power Supply
Board, see "Mi seel laneous Adjust-
ments."
(B) If the voltages are missing at Con-
nector J6, turn the Computer Off
and disconnect the power connectors
from the System Board and Disk
Drive. Connect a #1129 lamp to the
5.0V Source (pin 1 of Connector J6)
and a #93 lamp to the 12.0V Source
(Pin 9 of Connector J6). WARNING:
Operating the Power Supply without
a load may damage it. Turn the
Power Supply On and recheck the
voltages. If the voltages are
still missing, check Fuse F1 .
(C) If the correct voltages return, re-
connect the Power Supply to the
System Board and Disk Drives one at
a time until the Board or Drive
that is causing the Power Supply to
shutdown is found. WARNING: Be
sure Power supply is turned Off
when connecting to the System Board
or Disk Drive.
(D) Check the CPU IC (U36) and ROM IC
(U41) by substitution.
SYSTEM BOARD
(A) A program runs for a while, then
suddenly stops or becomes erratic
in operation. Check RAM IC Banks
and 1 (IC's U1 thru U16).
KEYBOARD
(A) Keyboard dead. Check Connector J4
on the System Board for good connec-
tions.
(B) Check the Keyboard cable and check
Connector CN on the Keyboard for
good connections.
(C) Check IC U22 on the System Board by
substitution.
VIDEO
(A) No video. Check Connectors J9 and
J10A for good connections and check
the Video cable going to the Mon-
itor.
©
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(B)
(C)
Check Video
tion.
IC (U30) by substltu-
Video display is not correct.
Check Video IC (U30) and Video RAM
IC's (U24, U31, U34 and U35).
SOUND
(A) No sound from the Internal Speaker
(SP1) and no audio at Connector
J10B. Check IC U37A by substitu-
tion.
(B) No sound from the Internal Speaker
(SP1). Check the setting of the
Volume Control (R26A) on the System
Board.
(C) If Volume Control is set properly,
check Connector J1 on System Board
for good connections and check
Speaker (SP1) voice coil for conti-
nuity.
DISK DRIVE
(A) Disk Drive operation Is erratic.
Clean the Drive heads. Check the
Drive Spindle Speed, see "Spindle
Speed Check".
(B) Check Connectors J1, J2, J4 thru J7
and J9 on the Disk Drive and Connec-
tor J5 on the System Board for good
connections.
(C) Drive dead. Check for 12V at pin 1
and 5V at pin 4 of Connector J2 on
the Drive Board. If the voltages
are missing, check the Power Sup-
ply.
CD) If the voltages are present at Con-
nector J2, check the setting of
Switch S2-3 on the System Board.
It should be set On.
(E) If Switch S2-3 is set On, check
IC's U22 and U37 on the System
Board by substitution.
PARALLEL PORT
(A) Paral lei Port does not work, check
Connector J7 for good connections.
(B) Check IC U55 by substitution.
IV
PRELIMINARY SERVICE CHECKS (Continued)
(D NORMAL/TURBO CPU CLOCK
(A) Run the following program to switch
the CPU clock speed each time a key
is pressed:
10 OUT 98,32:PRINT "NORMAL (4.77MHz)"
20 AS=!NKEYS:IF AS="" THEN 20
30 OUT 98,40:PRINT "TURBO (7.16MHz)"
40 AS=INKEYS:IF AS="" THEN 40 ELSE 10
Check for a logic Low at pin 37 of
IC U22 with the speed set to "Nor-
mal" and logic High with the speed
set to "Turbo". if the reading is
not correct, check IC U22.
(B) Check for a frequency of 4.77MHz at
pin 16 of IC U51 with the speed set
to "Normal" and 7.16MHz with the
speed set to "Turbo". If the fre-
quency does not switch, check IC
U51.
CABINET REMOVAL
DISASSEMBLY INSTRUCTIONS
SYSTEM BOARD REMOVAL
Remove two screws from lower front of cabinet.
Slide cabinet forward and up to remove.
REAR PANEL REMOVAL
Remove three screws from lower rear of rear
panel. Pull out on bottom of panel and lift
up to clear tabs on top to remove panel.
DISK DRIVE REMOVAL
Slide metal shield out of slot on left side of
Disk Drive bracket. Remove two screws from
left front, two screws from left rear and one
screw from right bottom of Disk Drive bracket.
Slide the Drives forward and unplug four con-
nectors from rear of Drives. Remove Drives
from Main Chassis. Remove four screws from
right side and two screws from left side of
Disk Drive bracket to remove Drives from
bracket.
POWER SUPPLY REMOVAL
Unplug Power Supply Connectors from System
Board and Disk Drives. Remove rear panel.
Remove four screws from rear holding Power
Supply to chassis and lift Power Supply out of
chassis.
Remove D i sk Dr i ves
four screws holding
remove left side,
from System Board.
and Power
left side
Supply. Remove
of chassis and
System Board.
System Board to bottom
board out of chassis.
POWER SUPPLY DISASSEMBLY
Disconnect Speaker
Remove plug- in boards
plug
from
Remove four screws ho I din
of chassis and I i
?f
Remove four screws holding Fan. Unplug and
remove Fan. Grip end of chassis next to AC
Power Connector, pull out to clear the tabs,
disconnect Connector SKI and remove the end of
chassis with On-Off Switch and AC Connector.
Remove four screws holding board to chassis
and remove board.
KEYBOARD DISASSEMBLY
Remove nine screws from bottom of Keyboard
cabinet and remove bottom of cabinet. Lift
Keyboard out of cabinet top.
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SWITCHES AND JUMPERS
SYSTEM BOARD
VIDEO AND INTERRUPT SWITCHES (S2)
ON
OFF
S2-1 Video
S2-2 Vertical Sync
S2-3 Floppy Disk Controller
S2-4 Parral lei Port
Color Graphics Video
(Internal or optional
CGA Board)
Enab ie Interrupt 5
Enab Ie I nterrupt 6
Enable Interrupt 7
Optional Monochrome
Video Board
Disable Interrupt 5
Disab Ie Interrupt 6
Disable Interrupt 7
RAM JUMPER
Remove jumper from pins El and E2 when installing additonal 256K RAM IC's.
(U5 thru U8 and U13 thru U16.5
8047 MATH CO-PROCESSOR JUMPER
Remove jumper from pins E3 and E4 when installing on 8047 Math Co-Processor
IC (U33).
PRELIMINARY SERVICE CHECKS (Continued)
LOW. NORMAL
HIGH, TURBO
J4 R26A J1
RAM RAM
BANK1 BANKO
VI
III
PRELIMINARY SERVICE CHECKS (Continued)
PREVENTATIVE MAINTENANCE
ENVIRONMENT
Computers perform best in a clean, cool area that is below 80 degrees Fahrenheit and free of
dust and smoke particles. Even though home Computers are not affected by cigarette smoke
as much as commercial Computers are affected, it is better to maintain a smoke-free area
around the Computer. Do not block cabinet vents of Computer, Monitor, Printer, or other
power devices.
ELECTRICAL POWER
Variations in the line voltage can affect the Computer. Try to avoid these fluctuations by using
an AC receptacle that is on a power line not used by appliances or other heavy current demand
devices. A power-surge protector, power-line conditioner, or non-interruptable power supply
may be needed to cure the problem. Do not switch power On and Off frequently.
KEYBOARD
Liquids spilled into the Keyboard can ruin it. Immediately after a spill occurs, disconnect the
Computer power plug from AC power outlet. Then, if circuitry or contacts are contaminated,
disassemble the Keyboard and carefully rinse the Keyboard printed circuit board with distilled
water and let it dry. Use a cotton swab to clean between the keys. Use a non-abrasive contact
cleaner and lint-free wipers on accessible connectors and contacts.
DISK DRIVES
Clean the read/write heads of the Disk Drives about once a month or after 100 hours usage.
Use only an approved head cleaning kit.
Handle carefully to preserve proper disk head alignment. A sudden bump or jolt to the Disk
Drives can knock the disk head out of alignment. If Disk Drive must be transported, place an
old disk in slot and close door during transport.
Store disks in their protective covers and never touch the disk surface. Observe the disk
handling precautions usually found on the back of disk protective covers.
PRINTERS
Carefully vacuum the Printer regularly. Wipe surface areas clean using a light all-purpose
cleaner. Do not oil the machine. The oil will collect abrasive grit and dust. The dust will act as
a blanket. This can cause components to overheat and fail.
STATIC ELECTRICITY
Static electricity discharge can affect the Computer. In order to minimize the possibility, use
anti-static mats, sprays, tools and materials, and maintain good humidity in the Computer en-
vironment.
MONITOR
Use an isolation transformer with any Monitor that does not come as part of the system since
some Monitors use a HOT chassis (chassis connected to one side of the AC line). The face of
the Monitor should never be left on for long period of time at high brightness level except when
pattern is being changed periodically. Use caution when cleaning anti-glare screens, to
preserve the glare-reduction feature.
VII
r:-fc^ Pi SERVICE CHECKS (Continued)
GH " : " >ERATING INS ',-UCTIONS
BOOT UP
insert a boat* le diskette Into Disk Drive A
and turn On the Computer. The Computer will
automatically boot up using the diskette In
Disk Drive A. If a MS-DOS (Microsoft Disk
Operating System) diskette is used, the Com-
puter will display the date and time and ask
for a new date and time. After the date and
time have been entered, the version of DOS
will be displayed on the Monitor screen along
with an A which indicates the DOS is run-
ning.
If Function Key F3 is pressed immediately
after the Computer beeps when turned On, the
Computer will boot up from a diskette Inserted
in Drive B.
MS-DOS
For a list of file names on the diskette fn
the current Disk Drive, type DIR and press the
ENTER key. To specify Disk Drive that is not
current (default), use DIR A: for Disk Drive A
or DIR B: for Disk Drive 8.
To return to MS-DOS from Basic, type SYSTEM
and press the ENTER key.
To load a (System) program from a diskette
while in DOS, type the program name and press
the ENTER key.
A blank diskette must be formatted before It
can be used to save information which Is in
memory. A formatted diskette must contain a
DOS or a Start-up program before the Computer
wll I boot up using that diskette.
Insert a diskette containing a "Format Pro-
gram" into Disk Drive A. Type FORMAT and
press the ENTER key. Follow the instructions
on the Monitor screen to 'format the unformat-
ted diskette. NOTE: Formatting a diskette
will wipe out any programs previously placed
on the diskette. The Computer automatically
defaults to Disk Drive A I f the destination
Disk Drive is not specified. Be sure to spec-
ify the destination Disk Drive of the diskette
to be formatted or the original diskette may
be ruined by the default action.
BASIC
When turned On, the Computer will come up In
MS-DOS as long as the MS-DOS diskette Is in
Drive A. The version of MS-DOS will appear at
the top of the screen.
The manufacturer also supplies Disk Basic on
diskette. To load Disk Basic, first boot up
DOS. Insert a diskette with Disk Basic pro-
gram on it. Type BASIC and press the RETURN
key or type BASICA and press the RETURN key to
load Disk Basic. To return to DOS from Basic,
type SYSTEM and press the ENTER key.
To view a list and the names of programs on a
diskette In the current Drive, type FILES and
press the ENTER key. Type FILES "Bs *•*" and
press the ENTER key to list programs from Disk
Drive B. Type FILES "A: *.*" to list programs
from Disk Drive A If it Is not the current (de-
fault) drive.
To load a program in Disk Basic or Advanced
Disk Basic from the diskette, type LOAD, the
program name enclosed in quotes, and press the
Enter Key.
To save a program, type SAVE, the program name
enclosed In quotes, and press the ENTER key.
To run a program from any Basic mode, type RUN
and press the ENTER key. To stop a program,
press the CTRL and BREAK (SCROLL LOCK) keys at
the same time. NOTE: Some programs will dis-
able or not recognize the CTRL and BREAK keys
to prevent the user stopping the program while
it is running.
RESETTING COMPUTER
Press the CTRL, ALT, and DEL keys, al I three
at the same time, to reset the Computer. The
Computer can also be reset by pressing the
Reset button on lower left front panel.
CHANGING OPERATING MODES
The Video, Disk Drive, and CPU speed modes can
be changed by pressing Function Keys F1 thru
F4 immediately after the Computer beeps when
it is turned On. Use the following chart to
determine the function of each Key:
F1 - Changes the Video mode to Monochrome
node. (Computer normally comes up In
Color Graphics mode.)
F2 - Changes the Video mode to TV mode.
F3 - Swaps Disk Drive references. Drive A
becomes Drive B and Drive B becomes Drive
A. The Computer will boot up from the
top Drive (normally Drive B).
F4 - Changes CPU speed to 4.77MHz. The Com-
puter normal ly comes up with a CPU speed
of 7.16MHz.
VOLUME CONTROL
A Volume Control (R26A) is provided on the
Main System Board to set the volume of the In-
ternal speaker. The cabinet must be removed
to gain access to the control.
VII!
PRELIMINARY SERVICE CHECKS (Continued)
CHASSIS ■ BOTTOM VIEW
HEADS
SPINDLE
mk
CHASSIS ■ TOP VIEW
IX
5j*/M5 COMPL'TERFACTS
TANDY
MODEL 1000SX
SYSTEM BOARD, KEYBOARD, POWER SUPPLY
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SAFETY PRECAUTIONS
See page 1 4
INDEX
Block Diagram.
Disassembly Instructions
General Operating Instructions...
GridTrace Location Guide
Power Supply Board
System Board
IC Pinouts and Terminal Gu
Line Definitions.....
LOgiC ChartS® . . e . a o a s ® e » a »
Miscel laneous Adjustments.
Pa r*T s list......... .......
ides.
.30 th
,.21 th
Page
. 41
, 14
. 13
, 29
, 11
.9,40
. 34
ru 33
38
ru 27
Page
Photos
Keyboard 36
Power Supply Board 28,35
System Board 1 0, 1 2, 37, 39
Safety Precautions 14
Schematics 2 thru 8, 42 thru 49
Schematic Notes 38
Switches and Jumpers 38
Test Equipment 15
Troubleshooting 15 thru 20
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Howard W. Sams 4 Co.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The listing of any available replacement part herein does not
constitute in any case a recommendation, warranty or guaranty
by Howard W. Sams & Co. as to the quality and suitability of
such replacement part. The numbers of these parts have been
compiled from information furnished to Howard W. Sams & Co.
by the manufacturers of the particular type of replacement part
listed. 87CS19008 DATE 9-87
Reproduction or use, without express permission, of editorial or pic-
torial content, in any manner, is prohibited. No patent liability is
assumed with respect to the use of the information contained herein.
© 1987 Howard W. Sams & Co.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206
U.S.A. Printed in U.S. of America
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12
A Howard W. Sams MI:MIIH:MJS Photo
SYSTEM BOARD
37
GENERAL OPERATING INSTRUCTIONS
BOOT UP
Insert a bootable diskette into Disk Drive A
and turn On the Computer. The Computer will
automatically boot up using the diskette in
Disk Drive A. If a MS-DOS (Microsoft Disk
Operating System) diskette is used, the Com-
puter will display the date and time and ask
for a new date and time. After the date and
time have been entered, the version of DOS
will be displayed on the Monitor screen along
with an A which indicates the DOS is run-
ning.
If Function Key F3 is pressed Immediately
after the Computer beeps when turned On, the
Computer will boot up from a diskette inserted
in Dr i ve B .
MS-DOS
For a list of file names on the diskette in
the current Disk Drive, type DIR and press the
ENTER key. To specify Disk Drive that is not
current (default), use DIR A: for Disk Drive A
or DIR B: for Disk Drive B.
To return to MS-DOS from Basic, type SYSTEM
and press the ENTER key.
To load a (System) program from a diskette
while In DOS, type the program name and press
the ENTER key.
A blank diskette must be formatted before it
can be used to save information which is in
memory. A formatted diskette must contain a
DOS or a Start-up program before the Computer
wil I boot up using that diskette.
insert a diskette containing a "Format Pro-
gram" into Disk Drive A. Type FORMAT and
press the ENTER key. Follow the instructions
on the Monitor screen to format the unformat-
ted diskette. NOTE: Formatting a diskette
will wipe out any programs previously placed
on the diskette. The Computer automatical ly
defaults to Disk Drive A if the destination
Disk Drive is not specified. Be sure to spec-
ify the destination Disk Drive of the diskette
to be formatted or the original diskette may
be ruined by the default action.
BASIC
When turned On, the Computer will come up in
MS-DOS as long as the MS-DOS diskette is in
Drive A. The version of MS-DOS will appear at
the top of the screen.
key or type BASICA and press the RETURN key to
load Disk Basic. To return to DOS from Basic,
type SYSTEM and press the ENTER key.
To view a list and the names of programs on a
diskette in the current Drive, type FILES and
press the ENTER key. Type FILES "B: *.*" and
press the ENTER key to list programs from Disk
Drive B. Type FILES "A: *.*" to list programs
from Disk Drive A if it is not the current (de-
fault) drive.
To load a program in Disk Basic or Advanced
Disk Basic from the diskette, type LOAD, the
program name enclosed in quotes, and press the
Enter Key.
To save a program, type SAVE, the program name
enclosed in quotes, and press the ENTER key-
To run a program from any Basic mode, type RUN
and press the ENTER key. To stop a program,
press the CTRL and BREAK (SCROLL LOCK) keys at
the same time. NOTE: Some programs will dls-^^
able or not recognize the CTRL and BREAK keys J 2*
to prevent the user stopping the program whilev/J
It is running. f\
RESETTING COMPUTER
Press the CTRL, ALT, and DEL keys, al I three
at the same time, to reset the Computer. The
Computer can also be reset by pressing the
Reset button on lower left front panel.
CHANGING OPERAT ING MODES
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The Video, Disk Drive, and CPU speed modes can
be changed by pressing Function Keys F1 thru
F4 Immediately after the Computer beeps when
It is turned On. Use the fol lowing chart to
determine the function of each Key:
F1 - Changes the Video mode to Monochrome
mode. (Computer normal ly comes up In
Color Graphics mode.)
F2 - Changes the Video mode to TV mode.
F3 - Swaps Disk Drive references. Drive A
becomes Drive B and Drive B becomes Drive
A. The Computer will boot up from the
top Drive (normally Drive B).
F4 - Changes CPU speed to 4.77MHz. The Com-
puter normal ly comes up with a CPU speed
of 7.16MHz.
VOLUME CONTROL
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The manufacturer also supplies Disk Basic on
diskette. To load Disk Basic, first boot up
DOS. Insert a diskette with Disk Basic pro-
gram on it. Type BASIC and press the RETURN
A Volume Control (R26A) is provided on the
Main System Board to set the volume of the In-
ternal speaker. The cabinet must be removed
to gain access to the control.
13
CABINET REMOVAL
DISASSEMBLY INSTRUCTIONS
SYSTEM BOARD REMOVAL
Remove two screws from lower front of cabinet.
Slide cabinet forward and up to remove.
REAR PANEL REMOVAL
Remove three screws from lower rear of rear
panel. Pull out on bottom of panel and lift
up to clear tabs on top to remove panel.
DISK DRIVE REMOVAL
Slide metal shield out of slot on left side of
Disk Drive bracket. Remove two screws from
left front, two screws from left rear and one
screw from right bottom of Disk Drive bracket.
Slide the Drives forward and unplug four con-
nectors from rear of Drives. Remove Drives
from Main Chassis. Remove four screws from
right side and two screws from left side of
Disk Drive bracket to remove Drives from
bracket.
POWER SUPPLY REMOVAL
Remove Disk Drives and Power Supply. Remove
four screws holding left side of chassis and
remove left side. Disconnect Speaker plug
from System Board. Remove plug-in boards from
System Board. Remove four screws holding
System Board to bottom of chassis and lift
board out of chassis.
POWER SUPPLY DISASSEMBLY
Remove four screws holding Fan. Unplug and
remove Fan. Grip end of chassis next to AC
Power Connector, pull out to clear the tabs,
disconnect Connector SKI and remove the end of
chassis with On-Off Switch and AC Connector.
Remove four screws holding board to chassis
and remove board.
KEYBOARD DISASSEMBLY
Remove nine screws from bottom of Keyboard
cabinet and remove bottom of cabinet. Lift
Keyboard out of cabinet top.
Unplug Power Supply Connectors from System
Board and Disk Drives. Remove rear panel.
Remove four screws from rear holding Power
Supply to chassis and lift Power Supply out of
chassis.
SAFETY PRECAUTIONS
1. Use an isolation transformer for servicing.
2. Maintain AC line voltage at rated input.
3. Remove AC power from the Computer system before servicing or installing elec-
trostatically sensitive devices. Examples of typical ES devices are integrated circuits and
semiconductor "chip" components.
4. Use extreme caution when handling the printed circuit boards. Some semiconductor
devices can be damaged easily by static electricity. Drain off any electrostatic charge on
your body by touching a known earth ground. Wear a commercially available discharging
wrist strap device. This should be removed prior to applying power to the unit under test.
5. Use a grounded-tip, low voltage soldering iron.
6. Use an isolation (times 10) probe on scope.
7. Do not remove or install boards, floppy disk drives, printers, or other peripherals with
Computer system AC power On.
8. Do not use freon-propelled sprays. These can generate electrical charges sufficient to
damage semiconductor devices.
9. This Computer system is equipped with a grounded three-pronged AC plug. This plug
must fit into a grounded AC power outlet. Do not defeat the AC plug safety feature.
10. Periodically examine the AC power cord for damaged or cracked insulation.
11. The Computer system cabinet is equipped with vents to prevent heat build-up. Never
block, cover, or obstruct these vents.
12. Instructions should be given, especially to children, that objects should not be dropped or
pushed into the vents of the cabinet. This could cause shock or equipment damage.
13. Never expose the Computer system to water. If exposed to water turn the unit Off. Do not
place the Computer system near possible water sources.
14
TEST EQUIPMENT
Test Equipment listed by Manufacturer illustrates typical or equivalent equipment used by SAMS' Engineers to obtain
measurements and is compatible with most types used by field service technicians.
TEST EQUIPMENT (COMPUTERFACTS)
Equipment
B & K Precision
Equipment No.
Sencore
Equipment No.
Notes
OSCILLOSCOPE
1570A,1590A,1596
SC61
LOGIC PROBE
DP51.DP21
LOGIC PULSER
DP101.DP31
DIGITAL VOM
2830,2806
DVM37,DVM56,SC61
ANALOG VOM
277,111,116
ISOLATION TRANSFORMER
TR1 10,1604,1653,1655
PR57
FREQUENCY COUNTER
1803,1805
FC71.SC61
COLOR BAR GENERATOR
1211A.1251, 1260,1249
CG25.VA62
RGB GENERATOR
1260,1249
FUNCTION GENERATOR
3020,3011,3030
HI-VOLTAGE PROBE
VOM/DMM
Accessory probes
HV-44
PR-28(HV)
HP200
TEMPERATURE PROBE
TP-28JP-30
CRT ANALYZER
467,470
CR70
DIGITAL IC TESTER
560,550,552
CAPACITANCE ANALYZER
LC53,LC75,LC76
LC77
INDUCTANCE ANALYZER
LC53,LC75,LC76
LC77
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TROUBLESHOOTING
POWER SUPPLY
NOTE: Do not operate the Power Supply without
a load. A #1129 lamp may be used as a load
for the 5.0V Source and a #93 lamp used for
the 12.0V Source. Use an, Isolation Transform-
er with a stepdown control when servicing the
Power Supply. Disconnect the Power Supply
from the System Board and Disk Drives to avoid
possible damage to the System from high volt-
ages that may be produced while servicing
Power Supply.
The Power Supply has a shutdown circuit, Zener
Diode D11, Optoisolator PHC2 and Shutdown Tran-
sistor (03). The circuit will shut down the
Power Supply if the 5.0V Source goes too high.
To determine if the Power Supply is In shut-
down, check for .67V at the base of Transistor
03. The shutdown can be defeated by removing
Zener Diode Dl 1 from the circuit.
WARNING: Defeating shutdown may allow high
voltages and currents to occur that may do
further damage to Power Supply. Use a current
limiting voltage stepdown AC Power Supply to
supply AC power to the defective Power Supply
when shutdown Is defeated.
When shutdown occurs, the charge on Capacitor
C9 will keep the Power Supply In shutdown if
it is turned Off and Immediately turned back
On. Turn the Power Supply Off and wait at
least two minutes before turning It back On to
allow the charge on Capacitor C9 to discharge.
Power Supply Dead. Check Fuse F1. If F1 is
open, check for possible shorts at Diode Dl
and check for a possible shorted Power Amp
Transistor (01). If Fuse F1 is good, apply AC
power and check for 120V AC across the AC in-
put pins of Diode Dl. If 120V AC is missing,
check Coils L1 and L3, Switch SI and Connector
SKI. If 120V AC Is present, check for 163V at
the collector of Transistor 01 . If 163V is
missing, check Diode D1, Thermistor R1 and
check the winding on Transformer T1 from pin 4
to pin 6 for continuity. If 163V is present,
check the waveform at the base of Transistor
Q1. If the waveform Is missing, check the
voltages and components associated with Oscil-
lator Transistor (Q2) and Transistor Q1 and
check the winding on Transformer T1 from pin 2
to pin 3 for continuity.
No -12.0V at pin 15 of Connector SK3-1. Check
the winding on Transformer T1 from pin 8 to
pin 9 for continuity and check the -12V Regula-
tor IC (IC2), Diode D10, Capacitors C23, C24
and Resistor R25.
No 12.0V at pin 7 of Connector SK3-1 . Check
for 13.3V at the emitter of the 12V Regulator
Transistor (Q4). If 13.3V is missing, check
the winding on Transformer T1 from pin 13 to
pin 14 for continuity and check Diode D8 and
Capacitors C16 and CI 7. If 13.3V is present,
check Error Amp IC (IC3), Transistor 04, Capac-
itors CI 8, C25, Resistors R22 thru R26 and
Control VR2.
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15
TROUBLESHOOTING (Continued)
No 5.0V at pin 9 of Connector SK3-1. Check
the winding on Transformer T1 from pin 11 to
pin 13 for continuity and check Diode D9,
Capacitors C19 thru C22 and Coil L2.
MICROPROCESSOR (CPU) OPERATION
Microprocessor IC (U36) not working. Check
for a 7.159MHz waveform at pin 19 of IC U36.
If the waveform Is missing, refer to the
"Oscillators and Dividers" section of this
Troubleshooting guide. If the waveform checks
good, check the logic reading at pin 21 (Re-
set) of IC U36 while turning the Computer On.
The reading should be High when the Computer
is turned On, then go Low. If the reading is
not correct, check the logic reading at pin 21
of IC U51 while turning the Computer On. The
reading should be High when the Computer Is
turned On, then go Low. If the reading is not
correct, check Capacitors C134 and C135, Diode
CR2, Reset Switch SI and Resistor R38. If the
reading is correct at pin 21 of IC U51, check
IC U51.
OSCILLATORS AND DIVIDERS
Verify Oscillator Modules (Y1 and Y2) are work-
ing properly by checking for a 28.636MHz sig-
nal at pin 27 and 16.0MHz signal at pin 14 of
IC U51. If the 28.636MHz signal is missing or
frequency is not correct, check Oscll lator
Module Y1 . If the 16.0MHz signal is missing
or frequency is not correct, check Oscll lator
Module Y2.
If the Oscillator Modules check good, check
the dividers In IC U51 by checking for a
1.193MHz signal at pin 3, 8.0MHz signal at pin
11, 14.318MHz signal at pin 12, 3. 5795MHz sig-
nal at pin 13, 7.16MHz (4.77MHz in normal
speed mode) signal at pin 16, 500KHz signal at
pin 38 and 4.0MHz signal at pin 39 of IC U51 .
If any of the signals are not correct, check
IC U51.
KEYBOARD
Keyboard does not function. Check Keyboard
Connector J4 on the System Board and Connector
CN on the Keyboard for good connections and
check the Keyboard Cable for broken wires. If
the Connectors and cable check good, check the
waveforms at pins 1 and 4 of Connector J4 on
the System Board while pressing the Space Bar
on the Keyboard. If the waveforms check good,
check IC U22 on the System Board. If the wave-
forms are missing, check the waveforms at pins
2, 21 thru 24 and 27 thru 34 of Keyboard Con-
trol I er IC (Ml) on the Keyboard. If the wave-
form Is missing at pin 22, check the 6.0MHz
Crystal (XL) and IC Ml. If any of the other
waveforms are missing, check IC Ml. If the
waveforms check good, check for pulses at pins
37 and 38 of IC Ml while pressing a key. If
pulses are missing, check IC Ml. If pulses
are present, check IC M2.
No Sound. If there Is no sound from the
Internal speaker, check the setting of the
Volume Control (R26A). The Control should be
set to Maximum clockwise for Maximum volume.
If the Control is set properly, type In and
run the following Basic program:
10 PRINT CHRS(7): GOTO 10
The program produces a continuous audio tone
of about 1100 Hertz. While the program is run-
ning, check for pulses at pin 13 of IC U19.
If pulses are missing, check IC U19. If
pulses are present, check for pulses at pin 6
of IC U20. If pulses are missing, check IC
U20. If pulses are present, check for pulses
at pin 13 of IC U51 . If pulses are missing,
check IC U51. If pulses are present, check
for the waveform shown In Figure A at pin 7 of
IC U37A. If the waveform is missing, check IC
U37A. If the waveform Is present, check for a
logic High at pins 26 and 27 and logic Low at
pin 28 of IC U22. If any of the readings are
not correct, check IC U22. If the readings
are correct, check for a logic High at pin 2
of IC U47. If the reading Is not correct,
check IC U47. If the reading Is correct,
check for the waveform shown In Figure A at
pins 9 and 10 of IC U25. If the waveform Is
missing
4V REF
Figure A
at either pin, check IC U25. If the waveform
is good at IC U25, check for the waveform
shown In Figure B at pin 1 of IC U26. If the
waveform Is missing, check the voltages and
components associated with IC U26. If the
waveform checks good, check for the waveform
shown in Figure C at pin 5 of IC U27 (with
Volume Control R26A set at Maximum volume).
If the waveform Is missing, check the voltages
and components associated with IC U27. If the
waveform checks good, check Capacitor CI 30,
Connector J1 and Speaker SP1 .
r r r
• 4V
5mSec
• 2V REF
Figure B
NORMAL/TURBO CPU CLOCK
Figure C
2V
. 5mSec
2V REF
To check the CPU clock switching circuits,
type In and run the following program:
10 OUT 98,32: PRINT "NORMAL (4.77MHz) H
20 AS=lhKEYS: IF AS= H " THEN 20
30 OUT 98,40: PRINT "TURBO (7.16MHz)"
40 AS=INKEYS: IF AS="" THEN 40 ELSE 10
16
TROUBLESHOOTING (Continued)
The program changes the clock speed each time
a key is pressed. Set the speed to "Normal"
and check for a logic Low at pin 2 and a fre-
quency of 4.77MHz at pin 16 of IC U51. Then
set the speed to "Turbo" and check for a logic
High at pin 2 and a frequency of 7.16MHz at
pin 16 of IC U51. If the readings are not cor-
rect at pin 2, check IC U22. If the frequency
does not switch at pin 16, check IC U51 .
PARALLEL PORT
Para I lei Port does not work. Check Connector
J7 for good connections. If the connector
checks good, disconnect any equipment connect-
ed to Connector J7 and type in and run the
following Basic program:
10 CLS
20 LOCATE 1,1
30 OUT 888,0:0UT 890,0
40 PRINT"A=";INP(888)
50 PRINT"B=";(INP(889) AND 248)
60 PRINT"C=»;INP(890)
70 OUT 888,255:0UT 890,255
80 PRINT"D=";INP(888)
90 PRINT"E=";(INP(889) AND 248)
100 PRINT"F=";INP(890)
110 GOTO 20
The program continuously checks the Para I lei
Port circuits and displays six numbers (A thru
F) on the Monitor screen. With nothing con-
nected to Connector J7, the following numbers
should appear on the Monitor screen:
A=0
B=88
C=203
D=255
E=88
F=244
The program displays the number 240 on the
Monitor screen when Joystick Connectors J2 or
J3 are not being used. The number will change
when pin 1 or 2 of Connector J2 or J3 is con-
nected to 5.0V or when pin 4 or 6 of Connector
J2 or J3 is connected to ground. Use the
fol lowing charts to determine what the number
will be.
Connected
To 5.0V
J2-1
J2-2
J 3-1
J3-2
Number
244
240
241
242
Connected
To Ground
J2-4
J2-6
J3-4
J3-6
Number
176
112
224
208
If the numbers are not correct, make the fol-
lowing checks while the above program is run-
ning. Check for pulses at pin 12 of IC U19.
If pulses are missing, check IC U19. If
pulses are present, check for pulses at pin 8
of IC U20. If pulses are missing, check IC^^
U20. If pulses are present, check for pulsesC/
at pin 10 of IC U53. If pulses are missing, {/J
check IC U53. If pulses are present, check^^
for the waveform shown In Figure D at pin 4 of j'
IC U17. If waveform is not correct, check \f)
Transistors 01 and 02, Zener Diode CR1, CapacI-«Ji
tor C1 18 and Resistors R12, R13 and R14. lf(Q
waveform is correct, connect pins 1 and 2 of
7.0V
1 OmSec
0V REF
Figure D
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Make a paral lei loopback test plug by connect-
ing together pins 17, 19, 21, 23 and 28 of a
34-pln female edge connector. Connect the
test plug to Connect J7 and run the above pro-
gram. The following numbers should appear on
the Monitor screen:
A=0
B=144
C=203
D=255
E=120
F=244
If any of the numbers are not correct, check
for pulses at pin 15 of IC U19 while the above
program is running. If pulses are missing,
check IC U19. If pulses are present, check IC
U55, Capacitors C152 thru C156 and C159 thru
C168 and Resistor Packs RP1 1 and RP12.
JOYSTICK PORTS
Joystick Ports do not work,
the following Basic program:
10 CLS
20 LOCATE 2,2
30 OUT 512,255
40 PRINT INPC513)
50 GOTO 20
Type in and run
Connectors J2 and J3 to 5.0V and check for
pulses at pins 1, 2, 13, and 14 of IC U17. If
pulses are missing, check the voltages and com-
ponents associated with IC U17. If pulses are
present, check IC U21, Capacitors C104, C105,
CI 08 and C109 and Resistor Packs RP1 and RP2.
USING A PRINTER FOR DISPLAY
If there is a defect In the CRT Controller
Board, information that is normally displayed
on the Monitor screen may not be visible or
readable. In such cases, it may be possible
to send the Monitor screen information to a
Printer that Is connected to the Computer.
While the Computer is in MS-DOS or GWBasic,
the Printer output can be turned On by press-
ing the Print Key. The Monitor screen Informa-
tion will continue to be printed out until the
Print Key Is pressed again to turn the Printer
Off. It Is also possible to get a printout of
the entire screen display by holding the Shift
Key down and pressing the Print Key.
Any Basic program that uses the PRINT command
to send Information to the Monitor screen can
be made to send the Information to a Printer
by changing the PRINT command to LPRINT.
17
TROUBLESHOOTING (Continued)
VIDEO
No Video. Check waveforms at pins 2, 6, 8 and
11 of IC U57. If any waveforms are missing,
check IC U30. If waveforms are good, check
waveform at the base of Video Amp Transistor
(03). If waveform is missing or not correct,
check IC U57, Capacitor C58 and Resistors R57,
R59, R61 and R62. If waveform is good, check
waveform at the emitter of Transistor 03. If
waveform is missing, check the voltages and
components associated with Transistor 03.
VIDEO SYNC
No vertical or horizontal sync on an RGB Moni-
tor. Check for a vertical waveform at pin 17
and a horizontal waveform at pin 15 of IC U57.
If either waveform is missing, check IC U30.
If waveforms are good, check IC U57, Capaci-
tors C169 and CI 71 and check pins 8 and 9 of
Connector J9 for good connections.
No vertical and horizontal sync on a Monitor
connected to the Composite Video Jack (J 10).
Check composite sync waveform at pin 11 of IC
U57. If waveform Is missing, check IC U30.
If waveform Is present, check for sync pulses
in waveform at the base of Video Amp Transis-
tor (03). If pulses are missing, check IC U57
and Resistor R61 . If sync pulses are present,
check Transistor 03, Capacitor CI 77, Resistor
R66 and Jack J 10.
VIDEO HIGHLIGHT
No Highlight. Type In and run the following
Basic program:
10 DEF SEG=&HB00
20 FOR X=0 TO 4000 STEP 2
30 POKE X, 42: POKE X+1,8
40 NEXT X
50 GOTO 50
The program fills the Monitor screen with
highlighted characters. While the program is
running, check for pulses at pins 4 and 16 of
IC U57. If pulses are missing at pin 4, check
IC U30. If pulses are present at pin 4 and
missing at pin 16, check IC U57. If pulses
are present at pin 16, check Resistors R58 and
R54 and Capacitor CI 74.
COLOR
No color or some colors missing. Type in and
run the following Baste program:
NOTE: Put four spaces between the quotes In
line 70.
10 DATA 9, 10,12
20 SCREEN 0,1:WIDTH 80
30 KEY 0FF:CLS
40 FOR Y=1 TO 3
50 READ C:OOL0R 0,C
60 FOR X=1 TO 160
70 PRINT » »;
80 NEXT X:NEXT Y
90 GOTO 90
The program puts blue, green and red horizon-
tal bars on the Monitor screen. While the pro-
gram is running, check for the waveform shown
in Figure E at pins 2, 6, 8, 12, 14 and 18 and
the waveform shown In Figure F at pins 7 and
13 of IC U57.
5V
20uSec
0V REF
5V
20uSec
0V REF
Figure E
Figure F
If waveforms are missing at pin 2, 6, 8 or 13
of IC U57, check IC U30. If waveforms are
present at pins 2, 6, 8 and 13 and missing at
pins 7, 12, 14 and 18, check IC U57. If wave-
forms are good at pins 7, 12, 14 and 18, check
Resistors R55 thru R58, R62 and R63, and Capac-
itors C58, C170, CI 72 and C173.
DISK DRIVE INTERFACE
WARNING: It Is possible for a defective Disk
Drive to write on or erase Information on a
diskette, even If the diskette is write pro-
tected. Check the Disk Drive by first using a
diskette that has programs that have been back-
ed up on another diskette. Do not leave the
alignment diskette in the drive while checking
voltages and waveforms unless specified In the
alignment procedures. The test equipment may
cause the Disk Drive circuits to erase sec-
tions of the alignment diskette even If the
diskette is write protected.
Check a I I setup jumpers and switches for cor-
rect positions and check all Interconnecting
cables for good connections.
WILL NOT READ
Insert a diskette containing data In Disk
Drive B and close the door. Type in and run
the fol lowing Basic program to keep the Disk
Drive running in read mode.
10 CLS
20 OUT 1014,128:007 1010,33:0UT 1010,37
30 OUT 1013,74:S=INP(1012)
40 OUT 1013,Y:S=INP(1012)
50 FOR X=1 TO 7
60 S=lhP(1013):S=lhP(1012):PRINT S
70 NEXT X: LOCATE 1,1
80 IF Y=1 THEN Y=5 ELSE Y=1
90 GOTO 20
To operate Drive A, change line
1014,128:OUT 1010,16:0UT 1010,20.
10 to OUT
The program displays seven numbers on the Moni-
tor screen. The numbers should change when a
diskette with data on it Is Inserted in the
Drive and the Drive door closed while the
above program Is running.
18
TROUBLESHOOTING (Continued)
If the numbers do not change, make the follow-
ing checks, while the program Is running with
a diskette In the Drive. Check for Index
pulses at pin 17 of Floppy Disk Controller IC
(U37). If pulses are missing, refer to the
"Index Sensor" section of this Troubleshooting
guide. If pulses are present, check for a
logic Low at pin 1 and logic High at pin 2 of
IC U48. If reading is not correct at pin 1,
check IC U37. If reading is correct at pin 1
and not correct at pin 2, check IC U48. If
readings are correct at IC U40, check for
pulses at pins 11 and pin 30 of Connector J5
for good connections and check the Drive
cable. If the connector and cable check good,
refer to the "Disk Drive Troubleshooting" in
the Disk Drive Folder.
If pulses are present at pin 11 of IC U45 and
missing at pin 12, check IC U45. If pulses
are present at pin 12, check for pulses at
pins 4, 19 and 26 of IC U37. If pulses are
missing at pins 4 or 19, check IC U51 . If
pulses are present at pins 4 and 19 and miss-
ing at pin 26, check IC U37. If pulses are
present at pin 26, check for pulses at pin 10
of IC U47. If pulses are missing, check IC
U47. If pulses are present, check for pulses
at pins 2 and 7 of IC U38. If pulses are miss-
ing, check IC U38 and Capacitor CI 33. If
pulses are present, check for pulses at pins
12 of IC U47. If pulses are missing, check IC
U47. If pulses are present, check IC U37.
WILL NOT WRITE
Insert a blank diskette Into the Disk Drive
and close the door. Type In and run the fol-
lowing Basic program which writes continuously
to the Diskette and displays a number on the
upper left corner of the Monitor screen. The
number should be when the Diskette is not
write protected and change to 2 when a write
protected Diskette is Inserted Into the Drive.
I f the numbers are not correct, refer to the
"Write Protect Does Not function" section of
this Troubleshooting guide.
10 CLS
20 OUT 1014, 128:0UT 1010,33:OUT 1010,37
30 S=INP(1012)
40 OUT 1013,77:S=INP(1012)
50 OUT 1013,Y:S=INP(1012)
60 OUT 1013,1 : S= I NP ( 1 01 2 )
70 OUT 1013,12:S=INP(1012)
80 OUT 101 3,1 2:S=I NPC101 2>
90 OUT 1013,0:S=INP(1012)
100 S=INP(1013):S=IN= (1012)
110 PRINT INPH013) AND 2:S=I NP( 101 2)
120 FOR X=1 TO 5
130 S=INP(1013):S=INP(1012)
140 NEXT X:L0CATE 1,1
150 IF Y=1 THEN Y=5 ELSE Y=1
160 GOTO 20
NOTE: This program will not write to the
diskette if the diskette Index sensor circuits
are not working. Check for Index pulses at
pin 11 of Buffer IC U4 while the Drive Is
running with a blank diskette Inserted. If
pulses are missing, refer to the "Index Sen-
sor" section of this Troubleshooting guide.
While the above program is running, check for
pulses at pins 4, 19, 25, 30, 31 and 32 of
Floppy Disk Controller IC U37. If pulses are
missing at pins 4 or 19, check IC U51. If
pulses are present at pins 4 and 19 and miss-
ing at pins 25, 30 31 or 32, check IC U37. If
a I I readings are correct, check for pulses at
pin 8 of IC U47. If pulses are missing, check
IC U47. If pulses are present, check for
pulses at pin 1 of IC U53. If pulses are miss-
ing, check IC U53. If pulses are present,
check for pulses at pins 9 and 8 of IC U48.
If pulses are missing at pin 9, check IC U50.
If pulses are present at pin 9 and missing at
pin 8, check IC U48. If pulses are present at
pin 8, check pin 22 of Connector J5 for good
connections and check the Drive cable. If the
connector and cable check good, refer to the
"Disk Drive Troubleshooting" in the Disk Drive
Fo I der.
WRITE PROTECT DOES NOT FUNCTION
Type in and run the program listed under the^}
"Will Not Write" section of this Troubles hoot- fi\
ing guide. The program will display the num-Hr
ber on the left upper corner of the MonitorvJ
screen if a diskette that is not write protect- (A
ed Is Inserted Into the Drive and the number 2^
if the diskette is write protected. fP>
WARNING: This program also writes on the
diskette. Do not use a diskette that has data
on It that Is Important. Insert a blank write
protected diskette Into the Drive and close
the door.
If the numbers on the Monitor screen are not
correct, make the f o 1 1 ow I ng checks w I th a
blank write protected diskette in the Drive
and the program running.
Check for a logic Low at pin 3 and logic High
at pin 4 of IC U45. If reading Is not correct
at pin 3, check pin 28 of Connector J5 for
good connections and check the Drive cable.
If the connector and cable check good, refer
to the "Disk Drive Troubleshooting" in the
Disk Drive Folder. If reading Is correct at
pin 3 of IC U45 and not correct at pin 4,
check IC U45. If reading is correct at pin 4
and the number on the Monitor screen Is not
correct, check the Floppy Disk Controller IC
(U37).
INDEX SENSOR
s
o
m>
o°
o <
o
c/>
X
To check the Index Detector circuits, insert a
diskette Into Drive A and close the door.
Type in and run the following Basic program to
keep the drive running or make all checks when
the Drive starts running after turning the
Computer On.
10 OUT 1014,128:0UT 1010,20:G0T0 10
While the Drive Is running, check for pulses
at pins 5 and 6 of IC U45. If pulses are miss-
ing at pin 5, check pin 8 of Connector J5 for
good connections and check the Drive cable.
If pulses are present at pin 5 and missing at
pin 6, check IC U45.
19
TROUBLESHOOTING (Continued)
TRACK 00 SENSOR
Disk Drive Head bangs against the Track 00
stop. Type In and run the following Baste
program to check the Track 00 detector cir-
cuits. The program will step the Head back to
Track 00 and display the number 16 on the Mon-
itor screen to Indicate the head Is on Track
00. If the head Is manually pushed off Track
00, the number should change to the number 0.
DRIVE A
10 OUT 1014,128:0UT 1010,16:0UT 1010,20
20 OUT 1013,7:S=INP(1012)
30 OUT 1013,1:S=INP(1012)
40 FOR T=1 TO 500: NEXT T
50 OUT 1014,1 28 :0UT 1010,16:0UT 1010,20
60 S=INP(1012)
70 OUT 1013,4:S=INP<1012)
80 OUT 1013,2:S=INP(1012)
90 CLSrPRINT INPC1013) AND 16:S=I NPdOl 2)
100 GOTO 40
If the numbers are not correct on the Monitor
screen, check (while program is running) for a
logic Low at pin 9 of IC U45 when the head Is
On Track 00 and logic High when the head is
Off Track 00. If readings are not correct,
check pin 26 of Connector J 5 for good connec-
tions and check the Drive cable. If readings
are correct, check for a logic High at pin 8
of IC U45 with the head On Track 00 and logic
Low with the head Off Track 00. If readings
are not correct, check IC U45. If readings
are correct, check for a logic High with
momentary pulses at pin 39 of Floppy Disk Con-
troller IC (U37). If reading Is not correct,
check IC U37. If reading Is correct, check
for a logic High with momentary pulses at pin
3 of IC U46 when the head is On Track 00 and
logic Low when the head Is Off Track 00. If
readings are not correct, check IC U46. If
readings are correct, check IC U37.
DRIVE SELECT AND DRIVE MOTOR
Drive A not being selected or Drive A and
Drive B Motors do not turn On. Type In and
run the following Basic program:
10 OUT 1014,128:OUT 1010,20:GOTO 10
While the program Is running, check for a
logic Low at pins 30 and 34 of Interface IC
CU22) and pins 2 and 6 of IC U49. If readings
are not correct at pins 30 or 34, check IC
U22. If readings are correct at pins 30 and
34 and not correct at pins 2 or 6, check IC
U49. If readings are all correct, check pins
10 and 16 of Connector J5 for good connections
and check the Drive cable. If the connector
and cable check good, refer to the "Disk Drive
Troubles hoot I ng" in the Disk Drive Folder.
Drive B not being selected. Type in and run
the following Basic program:
10 OUT 1014,128:0UT 1010,37:6OT0 10
While the program is running, check for a
logic Low at pin 3 and 4 of IC U49. If read-
ing Is not correct at pin 3, check IC U22. If
reading is correct at pin 3 and not correct at
pin 4, check IC U49. If reading Is correct at
pin 4, check pin 12 of Connector J5 for good
connections and check the Drive cable. If the
connector and cable check good, refer to the
"Disk Drive Troubleshooting" in the Disk Drive
Folder.
HEAD POSITION MOTOR
Head position motor not working,
run the following Basic program,
continuously alternates the head
between tracks 00 and 16.
DRIVE B
Type in and
The program
on Dr I ve B
10 OUT 1014,128:0UT 1010,33:0UT 1010,37
20 OUT 1013,7:S=INP(1012)
30 OUT 1013,1 :S=INP(1012)
40 OUT T=1 TO 500:NEXT T
50 OUT 1010,37
60 OUT 1013,15:S=INP(1012)
70 OUT 1013,1 :S=INP(1012)
80 OUT 1013,16:S=INP(1012)
90 FOR T=1 TO 500:NEXT T
100 GOTO 10
While the program Is running, check for pulses
at pins 37, 38 and 39 of Floppy Disk Control-
ler IC (U37). If putss are missing, check IC
U37. If pulses are present, check for pulses
at pin 11 of IC U46. If pulses are missing,
check IC U46. If pulses are present, check
for pulses at pin 4 and 6 of IC U48. If
pulses are missing, check IC U48. If pulses
are present, check pins 18 and 20 of Connector
J5 for good connections and check the Drive
cable. If the connector and cable check good,
refer to the "Disk Drive Troubleshooting" In
the Disk Drive Folder.
20
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25
PARTS LIST AND DESCRIPTION
When ordering parts, state Model, Part Number, and Description
ELECTROLYTIC CAPACITORS
ITEM
No.
RATING
MFGR.
PART No.
C1 18
MAIN BOARD
(SYSTEM)
.22 63V 10?
8393225
CAPACITORS
ITEM
No.
RATING
MFGR.
PART No.
C1
C2
POWER SUPPLY BOARD
.1 250VAC 20?
.22 250VAC 20?
XE-224
ITEM
No.
RATING
MFGR.
PART No.
C99
CI 23
SYSTEM BOARD
39 NPO 500V 5%
330 NPO 500V 5%
8301 332
COILS & TRANSFORMERS
ITEM
No.
FUNCTION
MFGR.
PART No.
OTHER
IDENTIFICATION
NOTES
LI
L2
L3
T1
Filter
RF Choke
Line Fi Iter
Switching
T0-9161-1
PSC-156
T0-4342
RESISTORS (Power and Special)
ITEM
No.
RU1
RATING
KEYBOARD
Resistor Network
POWER SUPPLY BOARD
R1
NTC 8 Cold
SYSTEM BOARD
R13
82. 5K \% 1/4W Metal Film
RP1
Resistor Network
RP2
Resistor Network
RP3
Resistor Network
RP4
Resistor Network
RP5
Resistor Network
RP6
Resistor Network
RP7
Resistor Network
RP8
Resistor Network
RP9
Resistor Network
RP10
Resistor Network
RP11
Resistor Network
RP12
Resistor Network
RP13
Resistor Network
REPLACEMENT DATA
MFGR.
PART No.
(1)
117-160-45201
160-13
D4FFL160P
8200382
8290210 (1)
8290032 (2)
8292310 (3)
8295033 (4)
8295033 (4)
8295033 (4)
8295033 (4)
8295033 (4)
8295033 (4)
8290016 (5)
8292246 (6)
8290044 (7)
8290010 (8)
NTE
PART No.
WORKMAN
PART No.
(1) 1000 x 5
(2) 10K x 5
(3) 10K x 7
(4) 33 x 4
(5) 150 x 7
(6) 4700 x 7
(7) 33 x 8
(8) 10K x 9
26
PARTS LIST AND DESCRIPTION (Continued)
When ordering parts, state Model, Part Number, and Description
CONTROLS (All wattages 1/2 watt, or less, unless listed)
ITEM
NO.
FUNCTION
RESISTANCE
MFGR.
PART NO.
NOTES
VR1
VR2
R26A
POWER SUPPLY BOARD
5 Adjust
12V Adjust
SYSTEM BOARD
Volume
2200
2200
1000
VGEK-PV(1S> 202B
H061 5-222B
VGEK-PV(IS) 202B
H061 5-222B
8279411
FUSE DEVICES
ITEM
NO.
DESCRIPTION
MFGR.
PART NO.
NOTES
DEVICE
HOLDER
F1
POWER SUPPLY
3 Amp § 250V
Fast Acting
MT4 3A 250V
P#5 722113
SPEAKER
ITEM
No.
TYPE
REPLACEMENT DATA ™~l
NOTES
MFGR.
PART No.
QUAM
PART No.
SP1
3" SO PM 8 Ohms
849001
30A05Z8
MISCELLANEOUS
ITEM
No.
PART NAME
MFGR.
PART No.
NOTES
KEY BOARD
L1
LED
CAPS, Green
L2
LED
Number Lock, Green
POWER SUPPLY
SW1
Sw i tch
Power
M5
Fan
SYSTEM
SI
Switch
Reset
S2
Switch
DIP
FBI
Ferrite Bead
FB2
Ferrlte Bead
FB4
Ferrite Bead
FBI 3
Ferrlte Bead
FB38
Ferrite Bead
thru
FB41
Y1
OscI 1 lator
8409039
28.63636MHz
Y2
Oscll lator
8409034
16MHz
o
Eh
o <
o
CO
X
CABINETS & CABINET PARTS (When ordering specify model, chassis & color)
ITEM
PART No.
Cabinet Top
Rear Panel
8719527
8719526
ITEM
PART No.
27
LO
♦ §3
•«5f .
*c:
CO
■HI
CM
• • ; ■
dr i
~M
tn
*zt
oo
CM
QQ
C3
Immmil
ImLmI
C3
POWER SUPPLY
28
A Howard W. Sams E3EB3Sffli photo
POWER SUPPLY GridTrace LOCATION GUIDE
ci
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
CI 3
CI 4
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D13
Fl
IC1
IC2
IC3
L1
L2
PHC1
PHC2
Q1
Q2
03
04
R1
R2
R3
R4
R5
R6
R7
R8
R9
RIO
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
C-1
E-1
G-2
F-3
G-3
E-3
A-9
F-4
B-11
E-5
B-4
B-6
C-6
F-5
A-13
D-10
C-10
C-1 4
E-1 1
E-1 2
E-1 2
E-1 4
F-12
F-13
C-1 2
F-1
A-4
E-5
B-4
B-6
F-5
F-5
C-9
E-9
G-11
A-13
F-6
B-1
A-12
F-9
C-1 1
D-1
D-13
A-11
B-11
C-6
C-8
C-8
B-9
D-1
A-4
C-4
F-6
B-8
B-8
B-6
B-5
G-5
G-5
G-5
E-6
A-10
A-12
A-15
B-1 2
B-1 3
B-1 2
B-7
B-7
C-1 3
C-10
C-1 3
C-1 3
F-13
R26
D-1 2
R27
E-10
R28
B-1 3
SKI
A-2
SK2
B-1 5
SK3
F-1 5
T1
E-8
VR1
B-1 3
VR2
C-1 2
m
o
>
z
o ■<
o
CO
X
29
LOGIC CHART
SYSTEM BOARD
PIN
IC
IC
IC
IC
IC
IC
IC
IC
IC
IC
IC
IC
NO.
U1
U2
U3
U4
U9
U10
U11
U12
U18
U19
U20
U21
1
P
P
P
P
P
P
P
P
P
P
L
H
2
P
P
P
P
P
P
P
P
P
H
L
H
3
P
P
P
P
P
P
P
P
P
H
L
P
4
P
P
P
P
P
P
P
P
P
L
P
H
5
P
P
P
P
P
P
P
P
P
P
H
P
6
P
P
P
P
P
P
P
P
P
H
H
L
7
P
P
P
P
P
P
P
P
H
P
L
P
8
H
H
H
H
H
H
H
H
H
L
H
L
9
P
P
P
P
P
P
P
P
P
P
H
P
10
P
P
P
P
P
P
P
P
L
H
H
L
11
P
P
P
P
P
P
P
P
L
H
H
L
12
P
P
P
P
P
P
P
P
L
H
*
P
13
P
P
P
P
P
P
P
P
P
H
*
L
14
P
P
P
P
P
P
P
P
P
H
H
P
15
P
P
P
P
P
P
P
P
L
H
H
16
L
L
L
L
L
L
L
L
P
H
P
17
P
H
18
P
P
19
P
H
20
H
H
PIN
IC
PIN
IC
PIN
IC
PIN
IC
PIN
IC
IC
IC
NO.
U22
NO.
U22
NO.
U23
NO.
U23
NO.
U24
U25
U28
1
L
21
H
1
P
21
H
1
P
H
P
2
H
22
H
2
P
22
H
2
L
L
P
3
H
23
H
3
P
23
P
3
L
L
P
4
L
24
L
4
P
24
H
4
H
*
P
5
L
25
H
5
P
5
P
H
L
6
*
26
L
6
P
6
P
L
H
7
P
27
L
7
P
7
P
L
L
8
P
28
L
8
P
8
P
L
P
9
P
29
L
9
P
9
H
L
*
10
P
30
H
10
P
10
P
H
*
11
P
31
H
11
H
11
P
H
*
12
P
32
H
12
L
12
P
H
L
13
P
33
H
13
P
13
P
H
*
14
P
34
H
14
H
14
P
H
H
15
H
35
L
15
P
15
L
H
16
P
36
L
16
L
16
P
H
17
P
37
H
17
H
17
L
18
H
38
L
18
P
18
L
19
P
39
L
19
P
20
H
40
H
20
P
30
LOGIC CHART (Continued)
SYSTEM BOARD
PIN
IC
PIN
IC
PIN
IC
PIN
IC
PIN
IC
PIN
IC
PIN
IC
NO.
U29
NO.
U29
NO.
U29
NO.
U29
NO.
U30
NO.
U30
NO.
U30
1
L
21
P
41
P
61
P
1
L
21
P
41
L
2
P
22
H
42
P
62
P
2
P
22
H
42
P
3
P
23
P
43
P
63
P
3
P
23
P
43
L
4
L
24
P
44
P
64
P
4
P
24
P
44
P
5
H
25
P
45
P
65
P
5
P
25
H
45
P
6
P
26
H
46
P
66
P
6
P
26
H
46
P
7
H
27
P
47
P
67
P
7
L
27
P
47
P
8
H
28
P
48
P
68
P
8
H
28
P
48
P
9
H
29
P
49
P
9
H
29
H
49
P
10
P
30
P
50
P
10
H
30
H
50
P
11
L
31
P
51
P
11
L
31
P
51
P
12
*
32
P
52
P
12
L
32
L
52
P
13
#
33
P
53
P
13
L
33
H
53
P
14
P
34
P
54
P
14
L
34
P
54
P
15
P
35
H
55
P
15
L
35
H
55
P
16
L
36
P
56
P
16
P
36
*
56
P
17
P
37
P
57
P
17
H
37
P
57
P
18
L
38
P
58
P
18
H
38
P
58
P
19
P
39
P
59
P
19
P
39
P
59
P
20
L
40
P
60
P
20
P
40
P
60
P
S
O
2-i
o ^
PIN
IC
PIN
IC
PIN
IC
IC
PIN
IC
PIN
IC
IC
IC
PIN
IC
NO.
U30
NO.
U30
NO.
U31
U33
NO.
U33
NO.
U34
U35
1136
NO.
U36
o
61
P
81
P
1
P
L
21
L
1
P
P
L
21
L
CO
X
62
P
82
P
2
P
P
22
P
2
P
H
P
22
P
63
P
83
P
3
P
P
23
L
3
P
H
P
23
L
64
P
84
P
4
H
P
24
P
4
H
H
P
24
P
65
P
-
5
P
P
25
P
5
P
P
P
25
P
66
P
6
P
P
26
P
6
P
P
P
26
P
67
P
7
P
P
27
P
7
P
P
P
27
P
68
P
8
P
P
28
P
8
P
P
P
28
P
69
P
9
H
P
29
»
9
H
H
P
29
P
70
P
10
P
P
30
*
10
P
P
P
30
H
71
P
11
P
P
31
P
11
P
P
P
31
P
72
P
12
P
P
32
L
12
P
P
P
32
P
73
P
13
P
P
33
P
13
P
P
P
33
L
74
P
14
P
P
34
H
14
P
P
P
34
H
75
P
15
P
P
35
P
15
P
H
P
35
P
76
P
16
P
P
36
P
16
P
P
P
36
P
77
P
17
L
*
37
P
17
P
L
L
37
P
78
P
18
L
*
38
P
18
L
L
P
38
P
79
P
19
P
39
P
19
P
39
P
80
P
20
L
40
H
20
L
40
H
31
LOGIC CHART (Continued)
SYSTEM BOARD
PIN
IC
IC
PIN
IC
PIN
IC
IC
IC
IC
PIN
IC
PIN
IC
IC
NO.
U37A
U37
NO.
U37
NO.
U38
U39
U40
U41
NO.
U41
NO.
U42
U43
1
P
L
21
P
1
P
P
P
H
21
P
1
P
P
2
P
P
22
P
2
P
P
P
P
22
L
2
P
P
3
P
P
23
P
3
P
P
P
P
23
P
3
P
P
4
H
P
24
P
4
L
P
P
P
24
P
4
P
P
5
P
P
25
P
5
L
P
P
P
25
P
5
P
P
6
H
P
26
H
6
L
P
P
P
26
P
6
P
P
7
H
P
27
L(3)
7
P
P
P
P
27
P
7
P
P
8
L
P
28
L(1)
8
H
P
P
P
28
H
8
P
P
9
L
P
29
H(1)
9
P
P
P
29
9
P
P
10
P
P
30
P
10
L
L
P
30
10
L
L
11
P
P
31
P
11
P
P
P
31
11
P
P
12
P
P
32
P
12
P
P
P
32
12
P
P
13
P
P
33
L(4)
13
P
P
P
33
13
P
P
14
P
P
34
L
14
P
P
L
34
14
P
P
15
P
P
35
H
15
P
P
P
35
15
P
P
16
H
P
36
K(1)
16
P
P
P
36
16
P
P
17
P
37
L(1)
17
P
P
P
37
17
P
P
18
P
38
L(6)
18
P
P
P
38
18
P
P
19
P
39
L(8)
19
P
P
P
19
P
P
20
L
40
H
20
H
H
P
-
20
H
H
PIN
IC
PIN
IC
PIN
IC
IC
IC
IC
IC
IC
NO.
U44
NO.
U44
NO.
U45
U46
U47
U48
U49
U50
1
P
21
H
1
*
L(8)
L
P
H
P
2
P
22
H
2
L
L(4)
H
P
H
L
3
H
23
P
3
H
L(4)
L
L(6)
L
L
4
P
24
L
4
L
P
H
HC7)
L
P
5
P
25
H
5
P
H
H
LCI)
L(10)
P
6
P
26
P
6
P
P
L
H(1)
L(10)
P
7
P
27
P
7
L
L
L
L
L
L
8
P
28
H
8
L(4)
P
P
P
H
L
9
P
9
H(5)
H
P
P
H
P
10
P
10
P
P
L
H<2)
*
P
11
P
11
P
L(1)
H
L(3)
*
P
12
L
12
P
L(8)
P
L
*
P
13
L
13
P
LCD
P
*
*
P
14
L
14
H
H
H
H
H
P
15
P
15
P
16
*
16
H
17
P
18
P
19
L
20
H
32
LOGIC CHART (Continued)
SYSTEM BOARD
PIN
IC
PIN
IC
PIN
IC
IC
IC
IC
PIN
IC
PIN
IC
IC
NO.
U51
NO.
U51
NO.
U52
U53
U54
U55
NO.
U55
NO.
U57
U57
1
H
21
H
1
P
P
P
H
21
H
1
P
L
2
H
22
L
2
P
P
P
L
22
L
2
H
P
3
P
23
P
3
P
P
L
P
23
H
3
P
P
4
L
24
P
4
P
H
P
P
24
P
4
P
L
5
L
25
P
5
P
*
P
H
25
L
5
P
P
6
P
26
L
6
P
*
P
L
26
H
6
P
P
7
P
27
P
7
P
L
P
H
27
#
7
P
P
8
P
28
P
8
P
H
P
L
28
H
8
P
P
9
P
29
P
9
P
P
P
H
29
H
9
H
P
10
H
30
P
10
L
L
L
L
30
P
10
L
L
11
P
31
P
11
P
*
P
H
31
H
11
*
P
12
P
32
P
12
P
*
P
L
32
P
12
P
P
13
P
33
P
13
P
H
P
H
33
P
13
P
P
14
P
34
H
14
P
H
P
H
34
P
14
P
P
15
H
35
H
15
P
P
L
35
P
15
P
P
16
P
36
H
16
P
P
H
36
P
16
P
L
17
P
37
H
17
P
L
H
37
P
17
P
P
18
P
38
P
18
P
P
L
38
P
18
H
P
19
P
39
P
19
P
L
H
39
P
19
P
L
20
P
40
P
20
H
H
L
40
H
20
H
H
KEYBOARD
PIN
IC
PIN
IC
PIN
IC
NO.
Ml
NO.
Ml
NO.
M2
1
»
21
P
1
H(1)
2
P
22
P
2
L(1)
3
P
23
P
3
L(1)
4
H
24
P
4
H(1)
5
H
25
H
5
H(1)
6
L(1)
26
H
6
L(1)
7
L
27
P
7
L
8
P
28
P
8
L(1)
9
H
29
P
9
H(1)
10
H
30
P
10
H
11
P
31
P
11
L
12
H
32
P
12
H
13
H
33
P
13
L
14
H
34
P
14
H
15
H
35
L
16
H
36
L
17
H
37
H(1)
18
H
38
H(1)
19
H
39
*
20
L
40
H
2
O
S- 1
•z
So
o <•
o
en
X
(1) Probe Indicates pulse when a key is pressed.
33
LINE DEFINITIONS
AAOTHRU AA7 Address
AEN Address Enable
ALE Address Latch Enable
AUDIO Audio Input Signal
BBIOR Input/Output Read
BBIOW Input/Output Write
BREQ Bus Request
BRESET Reset
BUFDIR Buffer Data Direction
BUFENB Buffer Enable
CAS Column Address Strobe, Memory
CLK Clock Timing Pulses
CLK358 Clock
CLK8M Clock
COL/MNO . . .Color/Monochrome, Monitor Operating Mode
CPUA08THRU CPUA19 CPU Address Bits 08 Thru 19
CPUADO THRU CPUAD7 CPU Data Bits Thru 7
CPUCLK CPU Clock
D4CLK Clock Pulse, 477MHZ
DACK1, DACK3 Direct Memory Access Acknowledge
DEN Data Enable
DIR Direction, Disk Read/Write Head
DMA/INTE Direct Memory Access Request/Floppy Disk
Controller Enable
DMATC Direct Memory Access Terminal Count
DORCLK Decode Latch Timing Signal
DRQ,DRQ1,DRQ3 Direct Memory Access Request
DS Disk Select
DSA, DSB Disk Drive Select A, B
ENBNMI Enable Non-Maskable Interrupt
FAST Clock Timing Select
FDCCHP Floppy Disk Controller Chip Select
FDCCLK Floppy Disk Controller Clock
FDCCS Floppy Disk Controller Chip Select
FDCDACK Floppy Disk Controller DMA Acknowledge
FDCDMRQ Floppy Disk Controller DMA Request
FDCINT Floppy Disk Controller Interrupt
FDCRST Floppy Disk Controller Reset
FDCTC Floppy Disk Controller Terminal Count
FDCWCK Floppy Disk Controller Timing Pulse
IA2 THRU IA7 Interrupt Request Lines 2 Thru 7
INDEX Index Sensor
INT Interrupt
INTA Interrupt Acknowledge
IOD0 THRU IOD7 Input/Output Data Bits Thru 7
IOR Input/Output Read
IOW Input/Output Write
JOYSTKS Joysticks
KBDINT Keyboard Interrupt
M/IO Select, Distinguishes Memory or I/O
MEMIOS Memory/Input-Output Select
MEMR Memory Read
MEMW Memory Write
MOTOR ON Disk Drive Motor On
MTREN Motor Enable, Floppy Disk
MTREN Motor Enable, Floppy Disk
MTRON Motor On, Disk Drive
MWEO Memory Write Enable, Bank
MWE1 Memory Write Enable, Bank 1
NMI Non-Maskable Interrupt
NMIEN Nonmaskable Interrupt Enable
OSC Oscillator
OSCOMA Oscillator Timing 14MHZ
PFAULT Parallel Port Fault State
PPACK Parallel Port Acknowlege
PPAUTOF Parallel Port Automatic Feed
PPBUSY Parallel Port Busy
PPDATAO THRU PPDATA7 . . Parallel Port Data Bits Thru 7
PPI/TIM Video Signal Timing
PPINIT Parallel Port Initialize, Set Up Sequence
PPINT Parallel Port Interrupt
PPPAEM Parallel Port Paper Empty Sensor
PPSTROB Parallel Port Timing Strobe
PRINTCS Chip Select
PSEL Port Select
QSO, QS1 Queue Status, Provide External Tracking
RAS Row Address Strobe
RDDATA Read Data
RDYIN „ Ready
READ DATA Read Data
READY Ready, Current Bus Cycle Is To Be Completed
REFRESH Refresh Dynamic Memory Pulses
RESET Reset
RFSH Refresh Address For Dynamic Memory
RQ/GT Request/Grant, Bus Control
SO, S1, S2 Function Status Characteristics
SELECT Select Line Indicates On Line Status
SIDE ONE Floppy Disk Side One Select
SIDESEL Floppy Disk Side Select
SNDCNTLO, 1,2 Sound Control Lines 0, 1, 2
SSO Status, Used For Decoding Current Bus Cycle
STEP Stepper Motor
SYSRST System Reset
TC Terminal Count
TMRINT Timer Interrupt Request
TRACK 00 Disk, Track 00 Sensor
V28MHZ Clock Pulse 28MHZ
VIDWAIT Video System Wait Signal
VSYNC Vertical Sync
WEN Write Enable
WR Write, Data Bus Info Stored In Memory Or I/O
WRDATA Write Data
WRITE DATA Write Data
WRITE GATE Write Gate
WRITE PROTECT Disk Overwrite Protection Sensor
WRPAT Write Protect, Overwrite Protection
34
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A Howard W. Sam. HIMUHJ&HmI Photo
POWER SUPPLY
35
o
LU
h-
O
z
00
CO
at
z
=3
a.
LU
i—
o
00
o
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o
CO
o
QC
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KEYBOARD
36
A Howard W. Sam. wM»|HftjVH| p h°'°
5.0V(B)
U10 U11
U53 U51 U56
12.0V(A) -12.0V 5.0V{A)
SOURCE SOURCE SOURCE
NOTE; ARROWS ON IC'S INDICATE PIN 1 UNLESS NOTED
2
3
B C
E V
R2 mm
VR1
Q3
-5.0V
SOURCE
o
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SYSTEM BOARD
12
A Howard W. Sams MI:MIIH:MJS Photo
SYSTEM BOARD
37
SWITCHES AND JUMPERS
SYSTEM BOARD
VIDEO AND INTERRUPT SWITCHES CS2)
S2-1 Video
S2-2 Vertical Sync
S2-3 Floppy Disk Control ler
S2-4 Parral lei Port
ON
Color Graphics Video
(Internal or optional
CGA Board)
Enable Interrupt 5
Enable Interrupt 6
Enable Interrupt 7
OFF
Optional Monochrome
Video Board
Disable Interrupt 5
Disable Interrupt 6
Disable Interrupt 7
RAM JUMPER
Remove jumper from pins E1 and E2 when instal ling additonal 256K RAM IC's.
(U5 thru U8 and U13 thru U16.)
8047 MATH CO-PROCESSOR JUMPER
Remove jumper from pins E3 and E4 when Instal ling on 8047 Math Co-Processor
IC (U33).
MISCELLANEOUS ADJUSTMENTS
POWER SUPPLY
NOTE: Do not operate the Power Supply without
a load.
5V ADJUSTMENT
12V ADJUSTMENT
NOTE: Perform the 5V Adjustment first. Con-
nect the input of a voltmeter to pin 7 of Con-
nector SK3-1. Adjust the 12V Adjust Control
for a voltage of 12.0V.
Connect the Input of a voltmeter to pin 9 of
Connector SK3-1. Adjust the 5V Adjust Control
(VR1) for a voltage of 5.0V. SCHEMATIC NOTES
^7 Isolated ground.
— *— Circuitry not used in some versions
Circuitry used In some versions
e See parts list
+ Ground
rrfn Chassis
Logic readings, voltages and waveforms
taken in Power Up mode. No diskettes in
Disk Drives. No keys depressed. Ver-
sion of compatibility software displayed
on screen along with "Insert System
Diskette and Strike any Key when ready".
Al I switches on DIP Switch S2 set On.
Voltages measured with digital meter.
Waveforms and voltages taken from
ground, unless noted otherwise.
Supply voltage maintained as shown at
Input.
Controls adjusted for normal operation.
Capacitors are 50 volts or less, 5% un-
less noted.
Electrolytic capacitors are 50 volts or
less, 20% unless noted.
Resistors are I/2W or less, 5% unless
noted.
Value in () used in some versions.
Measurements with switching as shown, un-
less noted.
DISK DRIVE INTERFACE AND DISK DRIVE NOTES
Voltages, waveforms and logic readings for the
disk drive interface and disk drive taken while
running the following Basic program. Readings
shown were taken when the disk drive head was
not moving unless noted.
10 OPEN "8: SAMS. DAT" FOR OUTPUT AS #1
20 FOR X=1 TO 300
30 PRINT #1, "HOWARD W SAMS"
40 NEXT X
50 CLOSE #1
60 GOTO 10
NOTE: Insert-
protected ) i n
gram.
a formatted diskette (not write
Drive B before running the pro-
CD
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
Is on track 00
Is on track 00
Probe Indicates P when head is moving.
Probe indicates L when head Is selected,
H when head 1 is selected.
Probe indicates H when head Is selected,
L when head 1 is selected.
Probe Indicates H when head
and L when off track 00.
Probe indicates L when head
and H when off track 00.
Probe indicates H when head
and L when head Is moving
center of the diskette.
Probe indicates L when head
and H when head is moving
center of the diskette.
Probe indicates H when head is moving.
Probe Indicates L when head Is moving.
is
out
is
out
mov I ng In
from the
moving In
from the
(10) Probe indicates H when Drive Motor is off.
38
SYSTEM BOARD
10
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SYSTEM BOARD
39
IC PINOUTS & TERMINAL GUIDES
SN74LS245N
P8088-2
9
10
01R
w
VCC
H
_^r~] r\_
3-i S
Al
[^(—4 J ENABLE
( rPI
B1
A2
rs7 )
( 3— M
B3
A3
r^7 (
) 3-^1
B3
A<4
r^ 7 / )
j >p-i
B4
A5
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r r?i
B6
A7
r^r r 1
r r?1
B7
AS
r^ ^
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BB
6NC
^J
U39,U40,U52
TRANSCEIVER
TOP VIEW
6ND
kj
vcc
AM
A15
A13
A16/S3
AI2
A17/S4
All
A1B/5S
A10
A19/S6
A9
sso
A8
MN/MX
AD7
RD
ADS
HOLD
ADS
AD4
HLDA
WR
AD3
I0/M
AD2
DT/R
AD1
dEn
ADO
ALE
NM1
IN7A
INTR
TEST
cut
READY
sw
RESET
(MAX NODE)
40
39
38
37
3E
35
34
33
32
8087
31 CR8/6T0)
30 CR8/6T1)
29 COOO
2B (52)
27 ran
26 SO)
25 (OSO)
24 CQS1)
23
22
21
SN74LS373N
OUTPUT CONTROL
<fv^
10
ID
^1
2
OE
6
a
0£
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80
3
20
20
V
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4
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a
a
70
5
60
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6
30
30
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8
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40
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E 6
\l ""
20
19
18
17
16
15
14
13
12
11
U42.U43
LATCH
TOP VIEW
U36
CPU
TOP VIEW
P8259A
vy
cs
VCC
uS
AO
w>
Tnta
D7
1R7
DB
1RB
D5
IRS
D4
1R4
03
IRS
02
IR2
D1
IR1
DO
IRO
CAS
INT
CAS 1
SP/EN
6ND
CAS 2
U44
INTERRUPT
CONTROLLER
TOP VIEW
SND
VCC
AD14
AD1S
AD13
A16/S3
AD12
A17/S4
AD11
A18/S5
AD10
A19/S6
AD9
AD8
WE/S?
P.0/6T1
AD7
INT
AD6
RO/GTD
ADS
NC
AD4
NC
AD3
S2
AD2
si
AD1
so
ADO
aso
NC
asi
NC
BUSY
cue
READY
SND
RESET
D8253C-S
V- 1
1
07
VCC
2
06
Rjf
3
OS
RD
4
04
CS
5
03
Al
6
02
AO
7
01
CLK2
8
DO
0UT2
9
CLKO
BATE2
10
OUTO
CLIO
11
SATEO
6ATE1
12
OND
0UT1
C074HCT138E
KEYBOARD
POWER SUPPLY
U33
COPROCESSOR
TOP VIEW
U23
TIMER
TOP VIEW
HC14529B
STRBX
VCC
XO
STRBY
XI
YO
X2
Y1
X3
Y2
A
Y3
B
II
GNn
Z
U25
INTERFACE
TOP VIEW
A
> — "^
VCC
fl
I
C
5—
Y1
62A
Y2
62B
Y3
81
Y4
Y7
Y5
GND
Y6
Y
U19
DECODER
TOP VIEW
SN74LS244N
V
U21,U54,US6,US7
BUFFER
TOP VIEW
D804BC
TO
VCC
XTAL 1
T1
XTAL 2
P27
RESET
P26
SS
P25
iSt
P24
EA
PI 7
RD
PI 6
PSEN
PIS
HR
PI 4
ALE
PI 3
DBO
PI 2
DB1
P11
DB2
P10
DBS
VDD
DB4
PR06
DBS
P23
DBS
P22
DB7
P21
6N0
P20
IC
2C
3C
(C
SC
6C
7C
314
313
312
311
310
39
3 8
6 1
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IC
2C
3C
3 6
3 5
3 4
s
1C3
BOTTOM VIEW
uuu
1 60
IC2
PHC2
TOP VIEW
M2
TOP VIEW
E C B
Q2.Q3
BOTTOM VIEW
FRONT VIEW
3 4
2C 3 3
O 1IDENT
PHC1
TOP VIEW
BCE
Q4
FRONT VIEW
M1
KEYBOARD
CONTROLLER
TOP VIEW
A ^,
UUU
BCE
Ql
DNT VIEW
KM41256-15
AS
"' 6ND
D IN
UE
CAS
D OUT
RAS
A6
AO
A3
A2
A4
A1
A5
VCC
A7
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U1 THRU U16
RAM
TOP VIEW
IC
□28
21=
327
3d
026
4C
32S
SC
324
6C
323
7C
S322
sp
C321
9C
b20
IOC
Pl9
11C
ai8
12C
317
13C
=316
14C
=315
U41
TOP VIEW
IC
2C
3C
4C
5C
6C
7C
BC
316
315
3H
313
312
311
310
39
U37A.U50
TOP VIEW
6 I
VR1
BOTTOM VIEW
ic
2C
3C
4C
5C
6C
7C
8C
9C
318
317
316
315
314
313
312
311
310
IC
2C
3CI
4C
SC
6C
7CT
SC
9C
IOC
11C
12C
13C
14C
ISC
ISC
17C
1BC
I9C
20 C
340
339
33B
337
336
335
334
333
332
331
330
329
328
327
326
325
324
323
322
321
IC
320
2C
319
3C
318
4G
317
SC
316
6C
pis
7C
314
8C
313
9C
p12
IOC
311
U18
TOP VIEW
IC
314
2p
313
3C|
312
4C
an
5p
310
SO
3 9
7C
3 8
U17,U20,U28
U45 THRU U49
US3
TOP VIEW
U22,U37,U51,U55
TOP VIEW
ic
2C
3C
4C
3 6
3 7
3 6
3 5
U24,U31,U34,U35
TOP VIEW
U26,U27,U38
TOP VIEW
E B C
Q1.Q3
BOTTOM VIEW
40
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PI
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AC
POLARIZED
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12.0V
2SA1441 rn
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A7AKEN FOM COMMON TIE POINT
PHOTO CI RCU] TRACE =
SCHEMATIC C1RCU1 TRACE = [TT|
TO
COMPUTER
POWER SUPPLY
42
A PHOTOFACT STANDARD NOTATION SCHEMATIC
with raronnrcra
© Howard W. Sams & Co. 1987
POWER SUPPLY
7
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PHOTO CIRCUITRACE =
SCHEMATIC CIRCU I TRACE = 11
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SOURCE
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C47 THRU C57 220pFT
CI 49, CI SO
C110
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C4Q.C131
C132,C136 :
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C12S1C242 THRU M44T
CI 37 THRU C142T C249,C251T
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SOURCE
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C148J
22MF1
C180,C146,C147.
VR2
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VOLT RE6
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SOURCE
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PHOTO CIRCUITRACE =
SCHEMATIC CIRCUITRACE =
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43
3 A
C074HCT02E
PART 0FUS3
RHOTO CIRCUITRACE =
SCHEMATIC CIRCUITRACE =
CABLING.
TUBE LINES REDUCE
USE OF MULTIPLE LINES
A PHOTOFACT STANDARD NOTATION SCHEMATIC
w,th HEHSEHH
© Howard W. Sams & Co. 1987
44
MAC
A e
IOD=
XMDO
XMD1
XMD2
XMD3
XMD4
XMD5
XMD6
XMD7
YMDO
YMD1
YMD2
YMD3
YMD4
YMD5
YMDS
YMD7
88 1 OR
38 10W
MEMR
CS
cc
dt
AOO
AOI
A02
A03
A04
A05
AOS
A07
A08
AOS
AOIO
A011
AOI 2
AOI 3
A014
AOI 5
AOI 6
A017
A018
AOI 9
IODO
I OD1
I0D2
I0D3
1004
IODS
IODE
I0D7
64
P
S3
P
62
P
61
P
60
P
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A PHOTOFACT STANDARD NOTATION SCHEMATIC
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A PHOTOFACT STANDARD NOTATION SCHEMATIC
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© Howard W. Sams & Co. 1987
TANDY
MODEL 1000SX
47
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TANDY
MODEL 1000SX
DISK DRIVE
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GrIdTrace Location Guide
Main Board..
IC Pinouts and Terminal Guides..
i-OCJ I C 0n3l r • ••»•*••••••••••«••**
rSPTS L. t ST» ••«•«•■••••«•••••«••<
Page
.10,11
.. 15
.. 15
.7,8,9
Photos
Chassis-Bottom Vie
Chassis-Top View..
Index Board
Main Board
Schematic. • . .
Schematic Notes
Troub leshoot Ing
Page
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Howard W. Sams 1 Co.
f m 4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S. A
The listing of any available replacement part herein does not
constitute in any case a recommendation, warranty or guaranty
by Howard W. Sams & Co. as to the quality and suitability of
such replacement part. The numbers of these parts have been
compiled from information furnished to Howard W. Sams & Co.
by the manufacturers of the particular type of replacement part
listed 87CS19008 DATE 9-87
Reproduction or use, without express permission, of editorial or pic-
torial content, in any manner, is prohibited. No patent liability is
assumed with respect to the use of the information contained herein.
© 1987 Howard W. Sams & Co.
4300 West 62nd Street, P.O. Box 7092, Indianapolis.Jndiana 46206
U.S.A. Printed in U.S. of America
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A PHOTOFACT STANDARD NOTATION SCHEMATIC
with BBgni
© Howard W. Sams & Co. 1987
TANDY
MODEL 1000SX
TROUBLESHOOTING
TEST SETUP
Connect a Disk Drive known to be operating
properly to the Computer as Disk Drive A.
Connect the defective Disk Drive as Disk Drive
B. Use Disk Drive A to load any alignment or
test program needed to check the defective
Disk Drive.
WARNING: It is possible for a defective Disk
Drive to write on or erase information on a
diskette, even if the diskette is write pro-
tected. Check the Disk Drive by first using a
diskette that has programs that have been back-
ed up on another diskette. Do not leave the
alignment diskette in the drive while checking
voltages and waveforms unless specified In the
alignment procedures. The test equipment may
cause the Disk Drive circuits to erase sec-
tions of the alignment diskette even if the
diskette is write protected.
switches for
I nterconnect-
Check a I I setup jumpers and
correct positions and check all
ing cables for good connections.
HEAD CLEANING INSTRUCTIONS
Use a cotton swab or lint- free cloth dampened
with 91? isopopyl alcohol and dry with a lint-
free cloth or use a non-abrasive cleaning
Diskette .
CONTINUOUS OPERATION OF DISK DRIVE
Use the following Basic program to keep Drive
A running continuously in the read mode.
Change the number 20 in the program to number
37 to make Drive B run continously.
10 OUT 1014,128:OUT 1010,20:GOT0 10
OSCILLATOR
Verify the oscillator Is working properly by
checking the 480KHz waveform at pin 37 of
Drive Controller IC (U3). If waveform Is
missing or the frequency not correct, check
Crystal Y1 , Capacitors C13 and C14, Resistor
RAB from pin 4 to pin 5, and IC U3.
WILL NOT READ
Insert a diskette containing data In Disk
Drive B and close the door. Type In and run
the following Basic program to keep the Disk
Drive running In read mode.
10 CLS
20 OUT 1014,128:0UT 1010,33:OUT 1010,37
30 OUT 1013,74:S=INP(1012)
40 OUT 1013,Y:S=INP<1012)
50 FOR X=1 TO 7
60 S=lhP(1013):S=INP(1012):PRINT S
70 NEXT X:L0CATE 1,1
80 IF Y=1 THEN Y=5 ELSE Y=1
90 GOTO 20
To operate Drive A, change line 10 to OUT
1014,128:0UT 1010,16:OUT 1010,20.
The program displays seven numbers on the Mon-
itor screen. The numbers should change when a
diskette with data on It is inserted In the
Drive and the Drive door closed. While the
above program Is running, check for a logic
High on the Write gate (pin 24) of Connector
J1 on the. Disk Drive Board to verify the Disk
Drive is In read mode.
If reading Is not correct, check the Disk
Drive Interface circuit on the Computer System
Board. If reading is correct, check for a
logic Low at pin 10 of Drive Controller IC
(U3). If reading is not correct, check IC U3.
If reading is correct, check the waveform at
pin 2 of Buffer IC (U4) while opening and
closing the Drive door (with diskette in
Drive). There should be a noticeable change
in the waveform as the Drive door Is opened
and closed. If there is no change, check the
head winding for continuity, check Connector
J9 for good connections, and check the volt-
ages and components associated with pins 1
thru 26 and 34 thru 44 of Read/Write Amp IC
(U5). If the waveform checks good at pin 2 of
IC U4, check for pulses at pin 3 of IC U4. If
pulses are missing, check IC U4. If pulses
are present, check the Drive cable and check
the Disk Drive Interface circuit on the
Computer System Board.
WILL NOT WRITE
Insert a blank diskette into the Disk Drive
and close the door. Type In and run the fol-
lowing Basic program which writes continuously
to the Diskette and displays a number on the
upper left corner of the Monitor screen. The
number should be when the Diskette is not
write protected and change to 2 when a write
protected Diskette is inserted into the Drive.
I f the numbers are not correct, refer to the
"Write Protect Does Not Function" section of
this Troubleshooting guide.
10 CLS
20 OUT 1014,128:0UT 1010,33:0UT 1010,37
30 S=INP(1012)
40 OUT 1013,77:S=1NP(1012)
50 OUT 1013,Y:S=INP(1012)
60 OUT 1013,1:S=INP(1012)
70 OUT 1013,12:S=INP(1012)
80 OUT 1013,12:S=INP<1012)
90 OUT 1013,0:S=INP(1012)
100 S=INPC1013):S=INP(1012)
110 PRINT INPC1013) AND 2: S=l NPdOl 2)
120 FOR X=1 TO 5
130 S=INP(1013):S=INP(1012)
140 NEXT X:L0CATE 1,1
150 IF Y=1 THEN Y=5 ELSE Y=1
160 GOTO 20
NOTE: this program will not write to the
diskette If the diskette index sensor circuits
are not working. Check for Index pulses at
pin 11 of Buffer IC <U4) while the Drive is
running with a blank diskette Inserted. If
pulses are missing, refer to the "Index Sen-
sor" section of this Troubleshooting guide.
While the above program Is running, check for
pulses at pins 22 and 24 of Connector J1. If
pulses are missing, check the Drive cable and
check the Disk Drive Interface circuits on the
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TROUBLESHOOTING (Continued)
>u!ses are present,
> (TP2) and 10 of
Computer System Board. If
check for pulses at pins
Drive Controller IC U3. If pulses are miss-
ing, check IC U3. If pulses are present,
check the head windings for continuity, check
Connector J9 for good connections, and check
the voltages and components associated with
pins 12 thru 27 of Read/Write Amp IC (U5).
WRITE PROTECT DOES NOT FUNCTION
Type In and run the program listed under the
"Will Not Write" section of this Troubleshoot-
ing guide. The program will display the num-
ber on the left upper corner of the Monitor
screen if a diskette that is not write protect-
ed is inserted Into the Drive and the number 2
If the diskette is write protected.
WARNING: This program also writes on the
diskette. Do not use a diskette that has data
on it that is important. Insert a blank write
protected diskette Into the Drive and close
the door.
While the program is running, insert a write
protected diskette Into the Drive and check
for a logic High at pin 5 of Connector J5. If
reading is not correct, check Connector J5 for
good connections and check the Write Protect
Sensor (PQ52). if reading Is correct, check
for a logic High at pin 4 and logic Low at pin
5 of Buffer IC U4. If reading Is not correct
at pin 4, check Drive Controller IC (U3). If
reading is correct at pin 4 and not correct at
pin 5, check IC U4.
INDEX SENSOR
To check the Index Sensor circuits, type In
and run the program given under "Continuous
Operation of Disk Drive" to keep the drive run-
ning. Insert a diskette In the Disk Drive and
close the door. Check for pulses at TP1 (pin
3 of Connector J5). If pulses are missing,
check Connector J5 for good connections, Resis-
tor RA7 from pin 2 to pin 1 and the Index Sen-
sor (PQ51). |f pulses are present, check for
pulses at pin 12 of the Buffer IC (U4). If
pulses are missing, check the Drive Controller
IC (U3>. If pulses are present, check for
pulses at pin 11 of IC U4. If pulses are miss-
ing, check IC U4. If pulses are present,
check pin 8 of Connector J1 for good connec-
tions.
TRACK 00 SENSOR
Disk Drive Head bangs against the Track 00
stop. Type in and run the following Basic
program to check the Track 00 detector
circuits. The program will step the Head back
to Track 00 and display the number 16 on the
Monitor screen to indicate the head is on
Track 00. If the head Is manually pushed off
Track 00 the number should change to the
number 0.
DRIVE A
40 FOR T=1 TO 500: NEXT T
50 OUT 1014,128:OUT 1010,16:OUT 1010,20
60 S=INP(1012)
70 OUT 1013,4: S= I NPC101 2)
80 OUT 1013,2:S=lhP(1012)
90 CLS:PRINT INPC1013) AND 16: S=l NPC101 2 )
100 GOTO 40
DRIVE B
10 OUT I014,128:0UT 1010,33:OUT 1010,37
20 OUT 1013,7:S=INP(1012)
30 OUT 1 01 3, 1 : S= I NP ( 1 01 2 )
40 T=1 TO 500:NEXT T
50 OUT 1014,128:OUT 1010,33:OUT 1010,37
60 S=INPC1012)
70 OUT 1013,4:S=INP(1012)
80 OUT 1013,2:S=INP(1012)
90 CLS:PRINT INPC1013) AND 16: S=l NP C 1 01 2)
100 GOTO 40
If the number on the Monitor screen is not cor-
rect, check for a logic High at TP3 when the
head is On Track 00 and a logic Low when the
head is Off Track 00. If readings are not
correct, check Connector J4 for good connec-
tions, check the Track 00 Sensor (M2) and
Resistor RA7 from pin 5 to pin 1. If readings
are correct, check for a logic High at pin 14
and a logic Low at pin 13 of Buffer IC (U4)
with the head On Track 00 and a logic Low at
pin 14 and ' a logic High at ptn 13 with the
head Off Track 00. If readings are not cor-
rect at pin 14, check Drive Controller IC
(U3). If readings are correct at pin 14 and
not correct at pin 13, check IC U4.
DRIVE MOTOR
Drive Motor will not run. Check Connectors J1
and J7 on the Disk Drive Board for good connec-
tions. Check for 5.0V at pin 4 and 12.0V at
pin 1 of Connector J2 on the Disk Drive
Board. If the voltages are missing, check the
power supply.
Type in and run the program given under "Con-
tinuous Operation of Disk Drive" to keep the
Drive running. Check for a logic Low at pin
16 of Connector J1 on the Disk Drive Board.
If reading Is not correct, check the Drive
cable and check the Disk Drive Interface on
the Computer System Board. If reading is
correct, check for a logic High at pin 3 of
Connector J7. If reading is not correct,
check the Drive Controller IC (U3). If
reading is correct, check Connector J7 for
good connections and check the Drive Motor
Control Board.
STEPPING MOTOR
Head position motor not working. Type In and
run the following Basic program. The program
continuously alternates the head on Drive B
between Tracks 00 and 16.
DRIVE A
10 OUT 1014,128:OUT 1010,16:0UT 1010,20
20 OUT 1013,7:S=INP(1012)
30 OUT 1013,1:S=INP(1012)
10 OUT 1014,128:0UT 1010,16:OUT
20 OUT 1013,7:S=INP(1012)
30 OUT 1013,1 :S=INPC1012)
40 OUT T=1 TO 500:NEXT T
1010,20
TROUBLESHOOTING (Continued)
While the program Is running, check for pulses
50 OUT 1010,20 at pins 18 and 20 of Connector J1. If pulses
60 OUT 1013,15:S=INP(1012) are missing, check the Drive cable and check
70 OUT 1 01 3, 1 : S= I NP C 1 01 2 ) the Disk Drive Interface circuit on the Com-
80 OUT 1013,16: S=l NPC1012) puter System Board. If pulses are present,
90 FOR T=1 TO 500:NEXT T check for pulses at pins 4 thru 7 of Motor
100 GOTO 10 Driver I C (U7). If pulses are missing, check
Drive Controller IC (U3). If pulses are pres-
DRIVE B ent, check for pulses at pins 10 thru 13 of IC
U7. If pulses are missing, check IC U7, Capac-
10 OUT 1014,128:OUT 1010,33:OUT 1010,37 itors C37 and C38, Connector J6, and check the
20 OUT 1013,7:S=INP(1012> Stepping Motor (Ml) windings for continuity.
30 OUT 1013,1 :S-lhF(1012)
40 OUT T=1 TO 500: NEXT T
50 OUT 1010,37
60 OUT 1013,15:S=INP(1012)
70 OUT 1013,1 :S=INPC1012)
80 OUT 1013,16:S=INP(1012)
90 FOR T=1 TO 500:NEXT T
100 GOTO 10
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GridTrace LOCATION GUIDE
C2
K-1
C4
J -3
C5
K-3
06
K-1 1
C9
G-3
C10
G-6
C13
F-11
C14
F-11
C17
D-2
C18
C-1
C19
D-2
C20
C-2
C21
F-7
C22
E-7
C23
D-7
C24
D-6
C25
D-6
C26
F-8
C28
D-9
C29
B-1
C32
B-4
C37
C-8
C38
B-8
CRA3
E-1
DSO
K-6
DS1
K-6
J1
M-8
J2
L-3
J4
J-1
J5
F-1
J6
C-10
J7
A-2
J9
G-1
L3
C-5
L4
B-3
L5
A-4
Q3
F-9
R1
E-3
R5
K-5
R6
K-7
R9
G-4
R11
F-4
R13
E-3
R14
D-2
R15
D-3
R16
C-3
R20
D-10
R21
D-11
R22
A-4
R23
B-8
RA1
L-9
RA3
J -5
RA4
1-5
RA5
K-9
RA6
1-10
RA7
G-3
RA8
G-1 1
RA9
E-6
RA11
C-2
TP1
C-4
TP2
C-5
TP3
C-5
TP4
C-5
TP5
C-6
TP6
C-6
TP7
C-6
TP8
C-7
U3
H-8
U4
H-11
U5
E-5
U7
E-10
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MFGR.
PART No./
TYPE No.
M2167
1 SS233F
DTA144EF
LH5060B
NB2803P
BA6581K
M54534P
ITEM
No.
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DISK DRIVE
CRA3
Q3
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U4
U5
U7
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PARTS LIST AND DESCRIPTION (Continued)
When ordering parts, state Model, Part Number, and Description
ELECTROLYTIC CAPACITORS
ITEM
No.
RATING
MFGR.
PART No.
C37
C38
DISK DRIVE
6.8 25V NP
6.8 25V NP
ITEM
No.
RATING
MFGR.
PART No.
CAPACITORS
ITEM
No.
RATING
MFGR.
PART No.
C21
C29
C32
DISK DRIVE
lOOpF 500V 2%
.0022 500V 2%
.0015 500V 2%
ITEM
No.
RATING
MFGR.
PART No.
COILS (RF-IF)
ITEM
No.
FUNCTION
MFGR.
PART No.
L3
L4
L5
DISK DRIVE
Peaking
Peak I ng
Peaking
ITEM
No.
FUNCTION
MFGR.
PART No.
CONTROLS (All wattages 1/2 watt, or less, unless listed)
ITEM
NO.
FUNCTION
RESISTANCE
MFGR.
PART NO.
NOTES
R1
DISK DRIVE
Balance
20K
RESISTORS (Power and Special)
ITEM
No.
RATING
REPLACEMENT DATA
MFGR.
PART No.
NTE
PART No.
WORKMAN
PART No.
R9
R22
RA1
RA3
RA4
RA5
RA6
RA7
RA8
RA9
RA11
DISK DRIVE
2670 \% 1/8W Carbon Film
200 \% 1/8W Carbon Film
Resistor Network
Resistor Network
Res I stor Network
Resistor Network
Resistor Network
Resistor Network
Resistor Network
Resistor Network
Resistor Network
(1)
(2)
(3)
(4)
(4)
(5)
(6)
(7)
(8)
(1) 1000 5h9
<2) 10K x 2, 56K x 2
(3) 56K, 10K, 1000, 2200 and 4700 x 2
(4) 10K x 4, 56K x 4
(5) 18K x 4
(6) 56K x 2, 1M x 1
(7) 22K, 39K, 15K, 150
(8) 150 x 2, 2000 x 2, 390
PARTS LIST AND DESCRIPTION (Continued)
When ordering parts, state Model, Part Number, and Description
MISCELLANEOUS
ITEM
No.
PART NAME
MFGR.
PART No.
NOTES
DISK DRIVE
LED51
M1
M2
M3
M4
LED
Motor
Sensor
Motor
Head
Activity, Red
Stepping
Track 00
Drive
Read/Write/Erase
PQ51
PQ52
Sensor
Sensor
Index
Write Protect
SCHEMATIC NOTES
<? Isolated ground.
— *— Circuitry not used in some versions
Circuitry used in some versions
e See parts list
+ Ground
"+" Chassis
Voltages, waveforms and logic readings for the
disk drive interface and disk drive taken while
running the following Basic program. Readings
shown were taken when the disk drive head was
not moving unless noted.
NOTE: Insert a formatted diskette (not write
protected) in Drive B before running the pro-
gram.
Terminal Identification may not be found
on unit.
Capacitors are 50 volts or less, 5% un-
less noted.
Electrolytic capacitors are 50 volts or
less, 20? unless noted.
Resistors are I/2W or less, 5% unless
noted.
Value In () used In some versions.
Measurements with switching as shown, un-
less noted.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
Probe indicates P when head is moving.
Probe Indicates L when head is selected,
H when head 1 is selected.
Probe Indicates H when head is selected,
L when head 1 is selected.
Probe indicates H when head Is on track 00
and L when off track 00. ...
Probe indicates L when, head Is on track 00 Voltages measured with digital meter
and H when off track 00.
Probe indicates H when
Logic Probe Display
L = Low
H = High
P = Pulse
* = Open (No lights On)
3
O
m>
o <
o
c/>
X
head is moving in
out from the
and L when head is moving
center of the diskette.
Probe Indicates L when head is moving in
and H when head is moving out from the
center of the diskette.
Probe indicates H when head is moving,
when head is moving.
s off.
Waveforms and voltages taken from
ground, unless noted otherwise.
Supply voltage maintained as shown at
i nput.
Controls adjusted for normal operation.
L if diskette
Probe indicates L
Probe indicates H when Drive Motor
Probe Indicates L when Drive Motor
Probe indicates
protected.
Probe indicates
protected.
Voltage varies when head is moving.
is off.
is write
H if diskette is write
10 OPEN "B: SAMS. DAT" FOR OUTPUT AS
20 FOR X=1 TO 300
30 PRINT #1, "HOWARD W SAMS"
40 NEXT X
50 CLOSE #1
60 GOTO 10
EQUIPMENT REQUIRED
ALIGNMENT
The speed
A lest program or a Disk Drive Tester Is
required which will turn On the Disk Drive,
select side or 1 and step the head to the
track specified In the alignment procedures.
Use a Dysan Analog Alignment Diskette 224/2A
when an Alignment Diskette Is specified In the
alignment procedures. NOTE: This alignment
diskette has only alignment patterns on It and
does not contain any alignment programs.
DRIVE TRACK PROGRAM
The following Basic programs can be used to
step the Disk Drive head to the Track
specified by the user. To stop the program,
press the Ctrl and Break keys.
NOTE: The programs select side only.
Operates Drive A
10 CLS
20 OUT 1014,128:OUT 1010,16:OUT 1010,20
30 OUT 1013,7:S=INPC1012)
40 OUT 1013,1: S=l NPC101 2)
50 INPUT "ENTER TRACK NUMBER "; TR
60 IF TR>40 THEN 50
70 OUT 1010,20
80 OUT 1013,15:S=INP(1012)
90 OUT 1013,1:S=INP(1012)
100 OUT 1013,TR:S=INP(1012)
110 FOR T=1 TO 400:NEXT T
120 PRINT"PRESS ANY KEY TO STOP"
130 A$=INKEY$:0UT 1010,20:IF A$="" THEN
ELSE 50
130
';TR
Operates Drive B
10 CLS
20 OUT 1014,128:0UT 1010,33:OUT 1010,37
30 OUT 1013,7:S=INP{1012)
40 OUT 1013,1:S=INP(1012)
50 INPUT "ENTER TRACK NUMBER
60 IF TR>40 THEN 50
70 OUT 1010,37
80 OUT 1013,15:S=INPC1012)
90 OUT 1013,1:S=INPO012)
100 OUT 1013,TR:S=INP(1012)
110 FOR T-1 TO 400:NEXT T
120 PRINT"PRESS ANY KEY TO STOP"
130 A$=INKEY$:0UT 1010,37: IF A$="" THEN
ELSE 50
SPINDLE SPEED CHECK
130
If a Disk Drive Tester which provides a
readout of the speed In rpm ts being used,
check for a speed of 300 rpm +4.5rpm.
If a Disk Drive Tester ts not available,
center and paste a strobe pattern on the Drive
motor on the bottom of the Disk Drive, see
Figure 1. Insert a diskette Into the Drive
and close the door. Type In and run the
program 1 1 sled under "Continuous Operation of
Disk Drive" to keep the Disk Drive running.
Use the outside pattern when 60 cycle
flourescent lighting Is used or the Inside
pattern for 50 cycle lights.
Is correct If the pattern appears to
stand stll I.
A*Y°fv
'/mi*
STROBE
PATTERN
Figure 1
RADIAL HEAD ALIGNMENT
Connect the channel A Input of a dual trace
scope to TP7, channel B to TP8, and the
external trigger Input to TP1. Connect ground
lead to TP6. Set the scope to add mode with
one channel Inverted, the sweep time to 20mSec
and the voltage range to .2V. Set both scope
Inputs 1o AC. Insert the Alignment Diskette
Into the Disk Drive and close the door. Turn
On the Disk Drive and step the head to track
16, Side 0. The cats-eye pattern shown In
Figure 2 should be displayed on the scope.
EQUAL AMPLITUDE
Figure 2
The amplitude of the two lobes displayed must
be within 70$ of each other. If the lobes are
out of tolerance, loosen two screws holding
Stepping Motor (M1). Adjust Motor until the
two lobes are equal In amplitude and tighten
Motor mount screws. Check the adjustment by
stepping the bead to Track 39 and back to
Track 16, then to Track 00 and back to Track
16, checking the lobes each time the head Is
on Track 16. Check the Track 00 Stop and
Detector adjustments after performing the
Radial Head Alignment. Select side 1 and
check Radial alignment of Head 1 using the
above procedures.
TRACK 00 SENSOR
Connect a scope to TP8 and set the sweep time
to 20uSec. Set the voltage range to .2V.
Insert the Alignment Diskette Into the Disk
Drive and close the door. Turn On the Disk
Drive and set the Head to Track 00. A 125KHz
stne wave should be displayed on the scope.
10
ALIGNMENT (Continued)
If the 125kHz signal Is not present, step the AZIMUTH CHECK
head forward or back until the 125kHz signal
Is present. When the 125kHz signal Is present
on the scope, the head Is on Track 00.
Connect the Input of a voltmeter to TP3.
Check for 5V when the Head Is on Track 00 and
0V when the Head Is on Track 02. If the
readings are not correct, set the Head to
Track 01, loosen the Track 00 Sensor (M2)
screw(see Disk Drive Mechanical Photo)on the
top of the Disk Drive and adjust the detector
until the voltmeter reading jumps fr^m 0V to
5V. Tighten the Track 00 screw and recheck
the Track 00 Sensor adjustment.
INDEX SENSOR ADJUSTMENT
Connect the channel A Input of a dual trace
scope to TP8, channel B Input to TP1 ( Index
pulse)and the scope ground to TP6. Set the
scope display to channel A with the voltage
range set to 20mV and the sweep time set -ho
50uS. Set the channel B Input to nonlnvertlng
mode and trigger the scope on channel B wtth
the trigger set to negative slope.
Insert the Alignment Dtskette In the Disk
Drive and close the door. Turn On Disk Drive,
select side and set the head to track 01.
Confirm that the leading edge of the burst
occurs 200uS ±200us after the leading edge of
the Index pulse, see Figure 3. If the Index
Sensor (PQ51) Is out of adjustment, loosen two
screws holding the board with the Index
detector on the top of the Disk Drive and
adjust the Board for 200ust200us,see Disk
Drive Mechanical, Top View Photo. If side
checks good, select side 1 and repeat the
above procedure to check Head 1.
Figure 3
Connect the channel A Input of a dual trace
scope to TP7, channel B Input to TP8, external
trigger Input to TP1 and connect the scope
ground to TP6. Set the scope to add mode with
channel B Inverted, sweep time to .5ms, AC In-
put, trigger to negative slope and voltage to
.1V range.
Insert the Alignment Dtskette, turn on the
Disk Drtve, select side and set the head to
track 34. Confirm that the pattern appears as
shown In Figure 4. The amplitude of bursts 1
and 4 must be equal to or less than the
amplitudes of bursts 2 and 3.
If the azimuth of Head checks good, select
side 1 and repeat the above procedure to check
the azimuth of Head 1.
Figure 4
READ CIRCUIT ADJUSTMENT
To do this adjustment a Disk Drive Tester or
program Is required that will continuously
write a 1F <62.5KHz) pattern on a blank
dtskette Inserted In the Drtve.
Connect the Input of a scope to pin 3 of IC U4
(Read Data Line). Set the sweep time to 2u
Sec, voltage range to 2V and trigger on
negative slope. Insert a BLANK dtskette In
the Drive and close the Drive door.
Continuously write a IF pattern to the
diskette. Two pulses should appear on the
scope screen. If the Phase AdJ Control (R1)
Is out of adjustment, the second pulse will
appear to be two pulses out of phase, see
Figure 5. If R1 Is out of adjustment, adjust
It until the second pulse appears to be one
pulse, see Figure 6.
2 pulses
2
o
S- 1
o <
o
w
X
Figure 6
11
c
•
: '' : •■(."
U5 U3 U7 03 U4
12.0V( ) 5.0V(C)
NOTE: ARROWS ON IC'S INDICATE PIN 1 UNLESS NOTED
A Howard W. Sams MhMHH.W^ Photo
12
LE061
5.0V(C)
o
m ^
■z
§ ■<
LOCATED ON OTHER SIDE OF THE BOARD
A Howord W. Scms MTWUirEreS Photo
13
TRACK 00
SCfiEW^
12-"
PQ51
I
IMI
mm
INDEX
SENSOR
SCREWS
m
It 11
iH
MNINi
<B
CHASSIS-TOP ¥IEW
14
LOGIC CHART
FLOPPY DISK DRIVE
PIN
IC
PIN
IC
PIN
IC
PIN
IC IC
PIN
IC
NO.
U3
NO.
U3
NO.
U3
NO.
U4 U5
NO.
U5
1
LC13)
21
P
41
LCD
1
L
21
2
H
22
L(4)
42
H(1)
2
P
22
3
L
23
L(13)
43
L(l)
3
P
23
4
*
24
H
44
H(1)
4
L(13)
24
5
H
25
H
45
H
5
H(12)
25
6
L
26
L
46
*(9)
6
H
26
7
H
27
L
47
H
7
L
27
H
8
H
28
L
48
L(4)
8
L
28
P
9
P
29
L
9
L
29
P
10
P
30
L
10
H
30
P
11
L(8)
31
H
11
P
31
H(2)
12
HC1)
32
L
12
P
32
H
13
H
33
L
13
H(5)
33
P
14
H
34
L
14
L(4)
15
L(10)
35
H
15
L
16
L
36
P
16
H
17
H(7)
37
P
18
H(1)
38
H
19
P
39
P
20
L
40
HC11)
TERMINAL GUIDES
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3 %s 5 W%i 3 WW%s / IDENT
nnnnnnnnnnn
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34 i=
p22
37 t=
35 C
=3 21
38 q
36 C
b20
39 1=
SVC
La 19
40 P
38 1=
=118
41 q
39 C
P 17
42 C
40 t=
=1 16
43 C
41 C
=115
44 C
42 C
bl4
451=
43 1=
o
pi 3
46 C
44 P
p12
4?C=
o
UULJULIUULiUULl
48 a
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1 2 3 4 S 6 7 8 910 11 12
TOP VIEW
TOP VIEW
m
8 C E
93
FRONT VIEW
15
■f
RADIAL
ALIGNMENT
SCREWS
. ■ :■:■;:.:■ ;:. ,;■ -... ■■ -v.: .-.- ;. ..■ ■;:■ :: ,■ .:■
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7 TP8
ii/
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f#i.;;i : jj/
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/ 1 /
PHASE
Ai,
I
ADJUST
• °
I
1
^-~R1
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mm 1
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CHASSIS ■ BOTTOM VIEW
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